ALBERT

Description: 〈p〉Publication date: 15 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 183〈/p〉 〈p〉Author(s): M. Kandidayeni, A. Macias, A. Khalatbarisoltani, L. Boulon, S. Kelouwani〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Proton exchange membrane fuel cell (PEMFC) models are multivariate with different nonlinear elements which should be identified accurately to assure dependable modeling. Metaheuristic algorithms are perfect candidates for this purpose since they do an informed search for finding the parameters. This paper utilizes three algorithms, namely shuffled frog-leaping algorithm (SFLA), firefly optimization algorithm (FOA), and imperialist competitive algorithm (ICA) for the PEMFC model calibration. In this regard, firstly, the algorithms are employed to find the parameters of a benchmark PEMFC model by minimizing the sum of squared errors (SSE) between the measured and estimated voltage for two available case studies in the literature. After conducting 100 independent runs, the algorithms are compared in terms of the best and the worst SSEs, the variance, and standard deviation. This comparison indicates that SFLA marginally outperforms ICA and FOA regarding the best SSE in both cases while it performs 20% and twofold better than other algorithms concerning the worst SSE. Furthermore, the obtained variance and standard deviation by SFLA are much less than the other algorithms showing the precision and repeatability of this method. Finally, SFLA is used to calibrate the model for a new case study (Horizon 500-W PEMFC) with variable temperature.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0360544219312848-egi10RTCKX882H.jpg" width="500" alt="Image 10882" title="Image 10882"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 15 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 183〈/p〉 〈p〉Author(s): Lifu Li, Zhongbo Zhang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In order to improve the natural gas engine (NGE) fuel economy, a steam direct injection method has been presented in the present study. In this method, exhaust was employed to heat water to produce superheated steam firstly. After that, at the power stroke, steam was injected into the cylinder directly. The potentials for fuel savings by this method are evaluated. First, ideal thermodynamic cycle of steam injected NGE is analyzed. Then, a baseline NGE is modeled and validated through experiments. After that, based on the simulation model, the effects of different steam injection parameters on the NGE performance are discussed, including steam mass, temperature and injected timing. The results show that the NGE fuel economy is significantly improved with steam direct injection. With optimal steam mass, 3.9–5.2% reductions of the NGE brake specific fuel consumption (BSFC) are obtained over different speeds, when steam temperature and injected timing are 550 K and 50 deg, respectively. Steam mass and injected timing have great influences on the NGE BSFC. However, steam mass is limited by pinch point temperature difference of the evaporator and exhaust temperature at the evaporator exit. In addition, steam injected timing is restricted by pressure inside the cylinder.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 183〈/p〉 〈p〉Author(s): Vinícius Faria Ramos, Olivert Soares Pinheiro, Esly Ferreira da Costa, Andréa Oliveira Souza da Costa〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Detailed model was proposed in this work for exergy analysis of a real biomass boiler. The model was based on an equilibrium model which uses Gibbs Energy minimization and energy balance to calculate the flue gas composition, the temperature of the furnace and the temperature of the flue gases along the boiler. The exergetic efficiency was calculated by the indirect method, and the exergy destruction in each component of the boiler and each material stream was evaluated. The Gibbs minimization model predicted successfully the complete combustion of the biomass and can be adapted to another thermochemical processes. The exergy analysis results showed that the furnace and the water walls have the higher exergy destruction, accounting for 47% and 30% of the total exergy destruction, respectively. In other parts of the boiler, the exergy destruction was higher in the water and steam flows than in the flue gases, and the results indicate that exergy destruction was higher in streams at lower temperatures. The global exergetic efficiency was 42.47%.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 183〈/p〉 〈p〉Author(s): Lin Yang, Xiang Ling, Hao Peng, LuanFang Duan, Xiaoyi Chen〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this study, a novel high temperature two-phase closed flat heat pipe receiver is proposed and investigated experimentally. In order to simulate the transient startup from frozen state, a transient analysis code for the novel flat heat pipe receiver has been developed. Closed-form analytical solutions for the temperature distribution along the heat pipe length are obtained and experimental tests are undertaken. These closed-form analytical solutions are in good agreement with the experimental data. The theoretical and experimental studies prove that the flat heat pipe receiver with sodium as working fluid has a well startup performance. Experiments were carried out to investigate the temperature uniformity of FHPR under the normal conditions. It is found that the FHPR has well feature of uniformity and stability through startup process experiments with constant heat flux. This research provides guidance for the research and development of flat heat pipe solar receiver, and has important significance for broadening its application in the field of heat utilization of solar energy at high temperature.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 183〈/p〉 〈p〉Author(s): Paweł Ocłoń, Marzena Nowak-Ocłoń, Andrea Vallati, Alessandro Quintino, Massimo Corcione〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This paper presents the determination of the heat losses of the pre-insulated pipe and twin pipe in the heating network. The paper compares the heat losses calculated by using the analytical solution (1D model) and numerical model (2D model) based on the Finite Element Method. The developed numerical model considered undisturbed ground temperature at various depths. Therefore, it allowed to study the effect of temperature distribution at various ground depths on heat losses in heating network. Various variants of insulation are considered including standard, plus and plus-plus types for pre-insulated tubes. The remaining heat loss calculation is based merely on temperature levels and thermal resistance factors (in the ground), determined by the pipe dimensions and materials. The differences in calculated heat losses by analytical and numerical model do not exceed 10%.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 183〈/p〉 〈p〉Author(s): Sobhan Badakhshan, Neda Hajibandeh, Miadreza Shafie-khah, João.P.S. Catalão〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Photovoltaic energy is one of the clean and efficient energies which has been developing quickly in the last years. As the penetration of solar plants is increasing in the electricity network, new problems have arisen in network operation. This paper models a high penetration factor of solar energy in the electricity network and investigates the impact of solar energy growth on both the generation schedule of different power plants and in the natural gas transmission network. Fuel management of gas power plants is modeled through simulation of the natural gas transmission network. To this end, an increase in the penetration of solar energy in the electricity network inevitably leads to a sudden increase in the output of gas fired units and a linear and integrated model with the electricity and the natural gas transmission networks has been presented to analyze both of them at the same time to better depict the impact of a high penetration of the solar energy in natural gas transmission grids. In this method, natural gas transmission network and Security Constrained Unit Commitment (SCUC) are presented in a single level program. Gas network constraints are linearized and added to the SCUC problem. The stress imposed on the gas network due to a sudden increase in the load of the electricity network is investigated. Conclusions are duly drawn.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 183〈/p〉 〈p〉Author(s): Bin Zhao, Mingke Hu, Xianze Ao, Nuo Chen, Qingdong Xuan, Yuehong Su, Gang Pei〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉For rooftop building-integrated photovoltaic (BIPV) technology, photovoltaic (PV) modules are typically mounted on the sunny side of a rooftop to receive a high amount of solar irradiance, whereas the opposite side of the rooftop will have free space. This study proposed a novel strategy for building-integrated PV and radiative cooling (RC) system, namely BIPV−RC system, by covering the sunny side of a rooftop with PV modules and its free side with all-day RC modules to integrate solar energy collection and RC utilization into a single building unit. A mathematical model was developed for the proposed BIPV−RC system and a case study was conducted in two tropical cities (Karachi, Pakistan and Riyadh, Saudi Arabia). Results show the total electricity and cooling output of the BIPV−RC system in Riyadh is 462.1 kWh·m〈sup〉−2〈/sup〉 and 1315.3 MJ m〈sup〉−2〈/sup〉, respectively, approximately 20.7% and 94.0% higher than those in Karachi. Moreover, a comparative study between the BIPV−RC system and the common BIPV and building-integrated RC (BIRC) system was performed and results indicate that the annual total energy output of the BIPV−RC system is nearly 79.1% and 16.8% higher than that of BIPV and BIRC system, respectively.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 183〈/p〉 〈p〉Author(s): Yuanwang Deng, Changling Feng, Jiaqiang E, Kexiang Wei, Bin Zhang, Zhiqing Zhang, Dandan Han, Xiaohuan Zhao, Wenwen Xu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Hydrocarbon(HC) emission from cold start for gasoline engine has become a big problem as the emission regulations go increasingly stringent. Zeolites are used to reduce hydrocarbon emission from gasoline engine before three-way catalysts reaching its operating temperature. In this paper, a mathematical model is fitted from hydrocarbons emission experimental data and a computational fluid dynamic(CFD) method is applied to investigate the influence on adsorption capacity of the different gasoline engine hydrocarbons catchers, and grey relational analysis is used to analyze and enhance adsorption performance of the gasoline engine hydrocarbon catchers for reducing hydrocarbons emission during the cold-start period. Driving cycle Federal Test Procedure(FTP) 75 is adopted to see the transient response of adsorbing hydrocarbon in cold start period. Results show that both hydrocarbon catcher length and its zeolite type in gasoline engine have great impact on hydrocarbon adsorption, the ranking of adsorption capacity is 25 cm  〉  20 cm  〉  15 cm, 5A 〉 13X. The gasoline engine hydrocarbon catcher with 25 cm length using zeolite 5A is of the best adsorption performance, and with this hydrocarbon catcher, the adsorption efficiency is 35.8% under cold start for driving cycle FTP75.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 183〈/p〉 〈p〉Author(s): Guihua Zhu, Lingling Wang, Naici Bing, Huaqing Xie, Wei Yu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The working fluids with higher solar thermal conversion performance within broadband spectrum ranges are of great concern for direct absorption solar collectors (DASCs). Both metal nanoparticles with localized surface plasmon resonance (LSPR) effects and carbon nanomaterials have unique spectral absorption behaviors and have shown better photothermal performance in DASCs. In this paper, we attempted to prepare composite nanofluids including plasmonic bimetallic alloy and carbon nanomaterials to realize enhanced solar absorption and photothermal conversion performance. By taking ZIF-8-derived nitrogen-doped graphitic polyhedrons (ZNGs) as carrier, plasmonic bimetallic Ag-Au alloy nanoparticles were loaded on them by an impregnation-reduction method successfully. Ag-Au/ZNGs ethylene glycol nanofluids showed significant broadband absorption in the visible and near-infrared spectrum range at a lower concentration. Comparing to ethylene glycol, the photothermal conversion effeiency of all ZNGs nanofluids increased remarkablely. Plasmonic bimetallic Ag-Au alloy nanoparticles further improved the photothermal conversion efficiency, which was up to 74.35% for Ag-Au ZNGs nanofluids compared with 72.41%, 70.35% for Au/ZNGs, Ag/ZNGs respectively. This work presents a new way to enhance solar energy absorption and improve solar thermal conversion efficiency of nanofluids for DASCs.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 183〈/p〉 〈p〉Author(s): Ruipeng Tan, Boqiang Lin, Xiying Liu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Market-oriented reforms on production factors in China are far lagged behind that of the commodity market, remaining the problem of price distortion in production factor markets. In this paper, we measure the degree of relative price distortion among capital, labor and energy focusing on China's secondary industry. Then, we take the own-price and cross-price elasticities as the link to estimate the demand changes of the three production factors in three cases. At last, we estimate the influence of relative price distortion elimination on the total factor energy efficiency. The main findings are: relative price distortions among the three factors exist. No matter taking the prices of capital, energy or labor as the benchmark, the prices of the other two kinds of production factors should be changed. Second, the own-price elasticities of the factors are negative, while the cross-price elasticities between the factors are positive, indicating the substitutability among the factors. Finally, correcting the relative price distortion can serve for the improvement of total factor energy efficiency of China's secondary industry. Therefore, if taking improvement of total factor energy efficiency as the goal, eliminating the price distortion in the factor market is necessary.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 183〈/p〉 〈p〉Author(s): Honglun Yang, Qiliang Wang, Yihang Huang, Junsheng Feng, Xianze Ao, Maobin Hu, Gang Pei〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Solar selective absorbing coatings that absorb solar irradiation and emit infrared radiation have a significant impact on the thermal efficiency of the receivers. The spectrum parameters heat transfer model and the non-ideal coating curve model are established. The cutoff wavelength of coatings is comprehensively optimized, and the effect of the optical properties of the coating on overall performance is analyzed. Results show that the optimal cutoff wavelength rises with the solar irradiation flux but decreases with increased absorber temperature. Sensitivity analysis results of the coating optical properties indicates that the thermal efficiency significantly decreases with increasing slope width. The change range of the thermal efficiency at the temperature of 200 °C is ±0.1%, resulting from a ±1 μm variation in slope width, whereas the range at 600 °C is ±6.5%. Spectral absorptivity analysis shows that the coating absorptivity has nearly same positive influence on thermal efficiency under different temperatures and irradiation fluxes, whereas emissivity analysis reveals an evidently different negative effect on the receiver performance. Finally, the annual optimal cutoff wavelength decreases with increasing temperature but increases with solar irradiation. The optimal cutoff wavelength decreases from 2.23 μm at 200 °C to 0.78 μm at 600 °C in Phoenix.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 183〈/p〉 〈p〉Author(s): Jing Yang, Zhiyong Zhang, Mingwan Yang, Jiayu Chen〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Recovering wasted heat is sustainable and cost-effective approach to secure energy supply in cities. This paper extended the Stackelberg game model to investigating the supply chain of the waste heat recovery market. Three models were proposed to investigate the optimal decision-making for different supply chain participants. With a validation case, the results suggested that the joint decision can reach the optimal outcomes and cost. Mobile heating strategy has advantages over coal-fired boilers, electric boilers, natural gas boilers in terms of costs and environmental protection. With a typical consumption of the recovered waste heat 342 GJ/day for water heating (from 25 °C to 60 °C) can save 11.672t standard coal and 79,800 RMB per day. In addition, improving thermal energy quality of waste heat recovery can generate higher profit and attract more potential customers.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 183〈/p〉 〈p〉Author(s): Xiaotian Lai, Minjie Yu, Rui Long, Zhichun Liu, Wei Liu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A modified theoretical model of dish solar Stirling engine was developed based on a Stirling cycle operating with finite shaft rotating speed and the energy balance equations at hot and cold ends. The convergence of solar receiver temperature and charged gas heat releasing temperature represent the stabilization of solar receiver and Stirling engine respectively, thus, to guarantee a steady operation of the overall system. Impacts of meteorological condition, operational parameter of Stirling engine on system performance were investigated and analyzed systematically. Results indicate that higher solar flux intensity improves system performance while wind deteriorates the system performance. With the input solar energy specified, optimal charged gas mass in Stirling engine exists corresponding to the maximal power output. More effective heater, regenerator and cooler contribute to better optimal system performance. Meanwhile, the charged gas mass optimized under the daily average solar flux intensity achieves the maximal mechanical work in a day with less computation. The maximal theoretical peak power output of 25 kW and overall efficiency of 44% are obtained as high performance heat exchangers are adopted and charged gas mass is optimized.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 183〈/p〉 〈p〉Author(s): Yu-Jen Wang, Chih-Kuang Lee〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this study, a two-degree-of-freedom (2-DOF) wave energy converter (WEC) composed of an eccentric dual-axis ring and power generators using circular Halbach array magnetic disks and iron-core coils was developed. The 2-DOF WEC was designed to convert kinetic energy from the pitching, rolling, and heaving motions of a mooring-less buoy. The eccentric dual-axis ring with appropriate weighting conditions enhanced power generation by revolving in biaxial hula-hoop motion, because it exhibited a higher angular velocity than when in swing motion. Kinetic equations for the biaxial eccentric dual-axis ring mounted on the buoy were derived using the Lagrange–Euler equation. Furthermore, weighting conditions of the eccentric dual-axis ring for biaxial hula-hoop motion were determined in accordance with frequency and amplitude of regular buoy motion. The magnetic flux density, cogging torque, and electromagnetic damping of the magnetic disk were evaluated using magnetic field strength simulations and Faraday's law of induction. The 2-DOF WEC prototype was implemented, and biaxial hula-hoop motion was observed in a wave flume test. An output power of 0.56 W was generated for the primary frequency of buoy motion from 0.7 to 1.0 Hz. Results indicate the WEC is feasible as a sustainable power source for sensors on buoys.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 183〈/p〉 〈p〉Author(s): Juan Ignacio Peña, Rosa Rodríguez〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This paper studies the realizability and compatibility of the three CEP2020 targets, focusing on electricity prices. We study the impact of renewables and other fundamental determinants on wholesale and household retail electricity prices in ten EU countries from 2008 to 2016. Increases in production from renewables decrease wholesale electricity prices in all countries. As decreases in prices should promote consumption, an apparent contradiction emerges between the target of an increase in renewables and the target of a reduction in consumption. However, the impact of renewables on the non-energy part of household wholesale electricity prices is positive in six countries. Therefore, decreases in wholesale prices, that may compromise the CEP2020 target of decrease in consumption, do not necessarily translate into lower household retail prices. Monte Carlo simulations suggest that the probability of achieving CEP's target of reductions in GHG emissions for 2020 is lower than 1% in Austria, Portugal, and Spain. In horizon 2030, Austria, France, Germany, Portugal, and Spain have probabilities lower than 1% of achieving the GHG emissions target. Finland and France present success probabilities lower than 1% on the national targets of renewable sources for 2020 and 2030 as do Austria and Spain with reductions in electricity consumption.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 187〈/p〉 〈p〉Author(s): Faezeh Esmaeili, Mohsen Gholami, Mohammad Hojjat〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this study, the external surface of a finned tube was coated by 13X zeolite powder, and the CO〈sub〉2〈/sub〉 adsorption equilibrium and dynamics were investigated experimentally. A slurry consisting of dionized water, 13X zeolite powder, and Acrylic latex emulsion (ALE) was used to coat the finned tube. The finned tube was coated by deep coating method. The equilibrium isotherms were measured at the range of 20–90 °C and fitted well by the dual-site Langmuir model. The average difference between the model and the results obtained from the experiments is about 2.5%. The nitrogen adsorption/desorption at 77 K was used for characterization of adsorbents. A 11% reduction was observed in pore volume and surface area. The dynamic test showed that the desorption of adsorbed CO〈sub〉2〈/sub〉 takes place in about 14 s which is an order of magnitude faster than the fastest developed method. A conservative criterion was developed for estimating adsorbent working capacity. This criterion showed that the working capacities of the adsorbent are about 80% of its ideal values.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0360544219317086-fx1.jpg" width="339" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 187〈/p〉 〈p〉Author(s): Saber Khanmohammadi, Shoaib Khanmohammadi〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉One of the most substantial aspects of the solar still systems that should be significantly considered is their economic and environment aspects. The present study deals with analyzing and identifying the behaviors of a cascade solar still desalination system in the presence of different insulation types and phase change materials. A Matlab code is developed to solve the energy equations for different components of the system simultaneously using ODE-45 solver. A comprehensive thermal, economic and environment analyses performed on the solar still desalination system with different insulation types and phase change materials. With selecting three objective functions namely total annual cost (〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.svg"〉〈mrow〉〈mi〉T〈/mi〉〈mi〉A〈/mi〉〈mi〉C〈/mi〉〈/mrow〉〈/math〉), exergy efficiency (〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si2.svg"〉〈mrow〉〈msub〉〈mrow〉〈mi〉η〈/mi〉〈/mrow〉〈mrow〉〈mi〉e〈/mi〉〈mi〉x〈/mi〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉), and exergy-based CO〈sub〉2〈/sub〉 mitigation 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si3.svg"〉〈mrow〉〈mrow〉〈mo stretchy="true"〉(〈/mo〉〈mrow〉〈msub〉〈mrow〉〈mi〉φ〈/mi〉〈/mrow〉〈mrow〉〈mi〉C〈/mi〉〈msub〉〈mrow〉〈mi〉O〈/mi〉〈/mrow〉〈mrow〉〈mn〉2〈/mn〉〈/mrow〉〈/msub〉〈mo〉,〈/mo〉〈mi〉e〈/mi〉〈mi〉x〈/mi〉〈mo linebreak="badbreak"〉−〈/mo〉〈mi〉b〈/mi〉〈mi〉a〈/mi〉〈mi〉s〈/mi〉〈mi〉e〈/mi〉〈mi〉d〈/mi〉〈/mrow〉〈/msub〉〈/mrow〉〈mo stretchy="true"〉)〈/mo〉〈/mrow〉〈/mrow〉〈/math〉, the tri-objective optimization is carried out for two considered cases of solar still desalination units. The thermal analysis represents that among different insulation types phenolic foam with 9.42 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si4.svg"〉〈mrow〉〈mi〉k〈/mi〉〈mi〉g〈/mi〉〈mo linebreak="goodbreak" linebreakstyle="after"〉/〈/mo〉〈msup〉〈mrow〉〈mi〉m〈/mi〉〈/mrow〉〈mrow〉〈mn〉2〈/mn〉〈/mrow〉〈/msup〉〈/mrow〉〈/math〉 per day has the highest value of distilled water production. The total annual cost analysis infers that the system with paraffin as phase change material (PCM) and glass wool as insulation, with 71.67 $, has the lowest TAC. The tri-objective optimization results demonstrate that for both considered cases three objectives are improved considerably compare with non-optimized solar still systems.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 183〈/p〉 〈p〉Author(s): Xiao Luo, Dongxu Wu, Congliang Huang, Zhonghao Rao〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉To relieve the fresh water shortage, a skeleton double layer structure (SDLS) is developed in this work to give a high evaporation efficiency for solar steam generation. In the SDLS, the bottom layer is dug hollow to prevent heat dissipating from the bottom layer into the bulk water. The method to optimize structure of the SDLS is also given in this work. The increase of height of SDLS has a positive effect on reducing heat losses while negative effect on supplying water, thus a proper height should be selected. After obtaining the proper height, the optimal cross sectional area of the skeleton structure can be approximately calculated based on the mass conservation of water. Applying the optimal SDLS, both of our experiment and simulation methods show that the evaporation rate and the evaporation efficiency under a solar power illumination of 1 sun can be 1.5 kg m〈sup〉−2〈/sup〉 h〈sup〉−1〈/sup〉 and 90% respectively, which is much higher than most emerging structures. The simulation by finite element method further shows that the high evaporation efficiency of the SDLS arrives from the low energy losses. The good match between the simulation and experimental results suggests the reliability of our results. We concluded that the SDLS is a promising system for application in solar steam generation due to its high evaporation efficiency, reusability and also easy to prepare.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 183〈/p〉 〈p〉Author(s): Giovanni Barone, Annamaria Buonomano, Francesco Calise, Cesare Forzano, Adolfo Palombo〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉This paper presents a novel dynamic simulation model for the analysis of a hybrid turboexpander system coupled with innovative high-vacuum solar thermal collectors. The model is developed in MatLab and it is able to dynamically calculate the energy, exergy, environmental, and economic performances of the investigated system, by taking into account the hourly fluctuation of thermodynamic and economic parameters (e.g. electricity cost, natural gas temperature, and flow rates, etc.). In addition, a computer-based Design of Experiment (DoE) approach was implemented for achieving the optimal design of the proposed system.〈/p〉 〈p〉A suitable case study is presented in order to show the capabilities of the developed simulation tool. Conventional and non-conventional decompression systems located in the weather zone of Messina (South-Italy) are investigated with the aim of assessing the optimal system configuration. By means of the computer-based DoE analysis, the optimal values of several design parameters (such as the number of solar thermal collectors, the volume of the hot water storage tank, and the size of the water loop pump) are calculated. Numerical results show significant primary energy savings (1.36 TWh/year) and avoided carbon dioxide emissions (348 t〈sub〉CO2〈/sub〉/year). From the economic point of view, a feasible simple pay-back period of 4.51 years is achieved. The destroyed exergy of the system components are calculated, obtaining the highest value for the turbo-expander, equal to 12.0 TWh/year.〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 183〈/p〉 〈p〉Author(s): Kamil Kozłowski, Maciej Pietrzykowski, Wojciech Czekała, Jacek Dach, Alina Kowalczyk-Juśko, Krzysztof Jóźwiakowski, Michał Brzoski〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The aim of this study is to analyse the possibilities of use of waste from dairy production to produce electricity and heat in the process of anaerobic digestion. The analysis covers one of the Polish dairies located in Eastern Poland. The amounts of the substrates produced in analyzed dairy plant will enable the production of approx. 14,785 MWh electricity and 57,815 GJ of heat. This will allow the construction of biogas plant with an electrical power of 1.72 MW. The paper has been stated that the construction of biogas plants for environmental and social reasons is beneficial.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 183〈/p〉 〈p〉Author(s): Dongran Song, Yinggang Yang, Songyue Zheng, Weiyi Tang, Jian Yang, Mei Su, Xuebing Yang, Young Hoon Joo〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This paper proposes a systematic method that precisely estimates the capacity factor (CF) of the variable-speed wind turbine (WT) by considering the coupled influence of the turbine operation constraints and the air density. To do so, the WT’s operation is defined by introducing the QN-curve (denoting the generator torque versus rotor speed), and the influence of different QN-curves on the power production is analysed while considering the influence of the air density. Then, a practical power-curve model considering the constraint of the QN-curve is derived for the WT. Following that, the formulation and the procedure of CF estimation are presented. Lastly, the presented CF estimation approach is applied into an industrial WT while considering the wind sites with four different altitudes. Finally, the application results show the capabilities of the proposed approach in evaluating the CF under the coupled influence of the QN-curve constraint and the air density. Meanwhile, comparing the proposed approach to four empirical approaches demonstrates that the CF estimation based on empirical models has considerable deviations to the results of the presented model under different site altitudes. Furthermore, among the four empirical models, the CF estimations from the quadratic and the linear models present the least deviations to those by the proposed model at the sites with low altitude and high altitude, respectively.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 183〈/p〉 〈p〉Author(s): Boqiang Lin, Hermas Abudu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Particularly for developing regions like Sub Saharan Africa, energy intensity is a critical policy issue and usually affected by four challenges: substitution between energy and other factors, technological change, changes in energy composition, and changes of economic growth. This paper examines energy intensity, output elasticity, energy-capital-labor substitution possibility, and factors contribution rates. The study applies a Translog production approach with data spanning 1990–2014 and further, applies ridge regression technique as a robust rectification to achieve unbiasedness in the findings. There is expected evidence of inverse relationship: higher energy intensity in lower per capita economy, evidenced by upward energy tariffs with lower energy elasticity. Factors are inelastic and have average elasticity substitution possibility for capital-energy with their inferential rebound effects’ challenges. However, other combinations indicate complementarity at the current development stage. We further, observe that if higher energy intensity not managed, would translate into higher CO〈sub〉2〈/sub〉 intensity, because 99% of total energy is sourced from hydrocarbons of 51% and 48% of biomass. Based on the findings, policymakers and implementors are encouraged to integrate and optimize the whole energy system towards improving energy efficiency through increasing renewable energy composition from the current 1% to at least 10% whiles increasing quality-energy from nonrenewable.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 183〈/p〉 〈p〉Author(s): Lanchuan Zhang, Jun Li, Yifei Wu, Mingyun Lv〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Solar energy is an essential energy source collected by photovoltaic (PV) cells for long-endurance stratospheric airships. Attitude control is crucial for the energy production of the PV array attached to the airship hull. This study was conducted to analyze the energy balance of stratospheric airships with attitude planning. A solar radiation and PV array model is proposed, then a steerable attitude strategy is established considering the roll, pitch, and yaw control of the PV array. The energy balance of the model is analyzed under an attitude planning scheme based on an actual airship design. The daily net energy of the airship is calculated according to monthly wind data of various latitudes. The influence on the net energy considering the conversion efficiency of PV cells and specific density of the energy stored system (ESS) is also analyzed. The results shows that attitude planning has a significant effect on both the energy production and wind resistance of the airship. The energy balance of the airship is markedly improved when PV conversion efficiency is high and ESS energy capacity is large. The results presented here may prove valuable for future stratospheric airship applications.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 183〈/p〉 〈p〉Author(s): Zhuochun Wu, Liye Xiao〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Accurate wind speed forecasting ensures the controllability for the wind power system. In this paper, a structure with density-weighted active learning (DWAL)-based model selection strategy from the perspective of meteorological factors is proposed to improve the accuracy and stability for wind speed deterministic and probabilistic forecasting. To improve training efficiency and accelerate the sample selection process, DWAL is employed. The multi-objective flower pollination algorithm is used to combine best models selected from model space with optimal weights for higher accuracy and stability. Except deterministic forecasts, as large-scale wind power generation integrated into power grid, the wind direction should also be forecasted and the estimation of the wind speed and direction uncertainty is vital, offering various aspects of forecasts for risk management. Thus, both deterministic and probabilistic forecasting for the wind speed vector are included in this paper. Eight datasets from Ontario Province, Canada, are utilized to evaluate forecasting performance of the model selection and the proposed structure. Results demonstrated: (a) the proposed structure is suitable for wind speed vector forecasting; (b) the proposed structure obtains more precise and stable forecasting performance; (c) the proposed structure improves the accuracy of deterministic forecasting and provides probabilistic information for wind speed vector forecasting.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 183〈/p〉 〈p〉Author(s): Matt Lewis, James McNaughton, Concha Márquez-Dominguez, Grazia Todeschini, Michael Togneri, Ian Masters, Matthew Allmark, Tim Stallard, Simon Neill, Alice Goward-Brown, Peter Robins〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Temporal variability in renewable energy presents a major challenge for electrical grid systems. Tides are considered predictable due to their regular periodicity; however, the persistence and quality of tidal-stream generated electricity is unknown. This paper is the first study that attempts to address this knowledge gap through direct measurements of rotor-shaft power and shore-side voltage from a 1 MW, rated at grid-connection, tidal turbine (Orkney Islands, UK). Tidal asymmetry in turbulence parameters, flow speed and power variability were observed. Variability in the power at 0.5 Hz, associated with the 10-min running mean, was low (standard deviation 10–12% of rated power), with lower variability associated with higher flow speed and reduced turbulence intensity. Variability of shore-side measured voltage was well within acceptable levels (∼0.3% at 0.5 Hz). Variability in turbine power had 〈1% difference in energy yield calculation, even with a skewed power variability distribution. Finally, using a “t-location” distribution of observed fine-scale power variability, in combination with an idealised power curve, a synthetic power variability model reliably downscaled 30 min tidal velocity simulations to power at 0.5 Hz (R〈sup〉2〈/sup〉 = 85% and ∼14% error). Therefore, the predictability and quality of tidal-stream energy was high and may be undervalued in a future, high-penetration renewable energy, electricity grid.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 187〈/p〉 〈p〉Author(s): Jian Chen, Xiong Pan, Canxing Wang, Guojun Hu, Hongtao Xu, Pengwei Liu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The airfoil research is one of the most essential issue which has great influence on the vertical axis wind turbine (VAWT) performance. Thus, a comprehensive research was conducted in this study with the objective of evaluating the effect of the twelve airfoils' controlling parameters on a Darrieus rotor's performance. The airfoil parameterization method, orthogonal algorithm and computational fluid dynamic (CFD) prediction were intergtated to fulfill this objective. A modification was conducted for the airfoil parameterization method to avoid trailing edge crossing and make controlling parameter's geometrical meaning more explicitly. The analysis results sorted the effect of design parameters by impact weight or contribution ratio. A remarkable finding was that the design parameters on the lower surface have greater influence than those on the upper surface. Orthogonal analysis gained a best airfoil whose power coefficient (C〈sub〉P〈/sub〉) is 13.26% larger than that of NACA 0015. Flow field analysis found that a tiny positive vortex was enlarged intensively with the increasing of the azimuth angle, which degrades the rotor's performance.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 187〈/p〉 〈p〉Author(s): Thi Anh Tuyet Nguyen, Shuo-Yan Chou〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉One of the most critical impediments of developing offshore wind systems is the high maintenance cost that reduces the cost-effectiveness of projects. To increase the cost-effectiveness of offshore wind energy, an effective solution is to reduce the overall maintenance cost by improving the efficiency of maintenance activities. Although maintenance optimization is crucial for improving cost-effectiveness, no model in the literature has analyzed the effects of government subsidies, the time value of money, the cost of lost power generation, and location on the optimal maintenance schedule. This study proposes an approach for thoroughly investigating the effects of various factors such as government subsidies, the time value of money, lost power generation, and location on maintenance cost. A dynamic approach was developed to determine the optimal maintenance schedule with the objective of minimizing the present maintenance cost on the time horizon. The results demonstrated that the optimal maintenance schedule varied according to changes in government subsidies under the influence of the time value of money. Moreover, the effect on the maintenance schedule became greater when government subsidies increased.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 187〈/p〉 〈p〉Author(s): Mohamed Adel Sayed, Mostafa R. Abukhadra, Mohamed Abdel Salam, Sobhy M. Yakout, Ahmed A. Abdeltawab, Ibrahim M. Aziz〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Novel heulandite/polyanailine@Ni〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 composite (Hu/PAN@NiO) was fabricated as an advanced product of enhanced photocatalytic properties and low band gap energy for efficient hydrogen generation. The composite was characterized and identified through different techniques including XRD, HRTEM, SEM, and FTIR in addition to the investigation of its textural and optical properties. The fabricated composite is of a significantly high surface area (531 m〈sup〉2〈/sup〉/g) and low band gap that reaches about 1.46 eV which strongly qualifies the product electrode in photo-electrochemical hydrogen generation processes. The synthetic composite exhibits effective photocatalytic performance in the photoelectrochemical splitting of water under a visible light source. The detected photocurrent density reached 4.7204 mAcm〈sup〉−2〈/sup〉 and the hydrogen production rate was estimated to be 4.1 μmol/h〈sup〉−1〈/sup〉cm〈sup〉−2〈/sup〉 after about 50 min at an applied voltage of +1V. The obtained results reflected the potentiality of such hybrid material as an effective catalyst in the photo-electrochemical splitting of water for hydrogen production.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 187〈/p〉 〈p〉Author(s): Mathieu Legrand, Luis Miguel Rodríguez-Antón, Carmen Martinez-Arevalo, Fernando Gutiérrez-Martín〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The European energy transition implies a relevant increase of renewable energies in the electric power generation mix. Integrating additional renewables is becoming more challenging due to their variability. Spain's peninsular situation aggravates this problem because it is an electric island. Within this framework, Liquid Air Energy Storage (LAES) is a promising technology for balancing the power grid. This work proposes a transient thermodynamic modelling of a 100 MW LAES plant. The cycle incorporates a packed-bed cold-storage system to enhance the charge/discharge efficiency. The appearance of a thermocline in the cold-storage unit is relevant regarding the round-trip efficiency. An economic study based on the simulation results is performed considering different scenarios of renewables grid penetration (photovoltaic and wind power). Depending on the installed LAES capacity, the levelized cost of delivered energy is evaluated. The results suggest that it is more interesting to store photovoltaic energy in the daytime peak hours and release energy during the night-time valleys to maximize the use of storage plants. This allows the levelized cost of energy and storage to be reduced to values as low as 150 and 50 €/MWh respectively. These prices are competitive with compressed air energy storage and even with pumped-hydro storage.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S036054421931655X-egi102Q5CTF2PS.jpg" width="367" alt="Image 10252" title="Image 10252"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 187〈/p〉 〈p〉Author(s): Salim Issaadi, Wassila Issaadi, Abdelkrim Khireddine〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉To increase the power output of a PV module or a field of PV modules, an electronic controller is incorporated between the PV generator and the load, whose role and main objective is the continuous monitoring of the maximum power point of the PV generator commonly known as MPPT (Maximum Power Point Tracking) and this in general per action on a DC-DC conversion device.〈/p〉 〈p〉The regulation and control techniques provide the impedance matching function, transferring to the load the maximum electrical power output from the PV generator in any the temperature and sunshine conditions.〈/p〉 〈p〉The development of a revolutionary method based on neural algorithms for the prediction of an instantaneous command is the main objective in our work.〈/p〉 〈p〉Indeed, the paper presents a new control strategy for the photovoltaic PV, it is a command based on Neuronal Network technique. It is the first time that this technique has been introduced, and proposed by the authors in synthesizing control laws for the converters of electronic power.〈/p〉 〈p〉The new technical algorithm based on Neural Networks, is designed to be more robust in performance with respect to tracking speed and precision.〈/p〉 〈p〉Moreover, this new successful technical research, provides a robust neural structure compared to the noisy empirical data used for the prediction of the command. Consequently a smooth control signal without oscillation, targeting exactly the expected optimal control with an independent control of the sampling frequency of the system.〈/p〉 〈p〉This study, which is followed by a simulation, has enabled us to consolidate the idea that the new Neural Network controller when compared to their classical counterparts, and obtains the best performances concerning the speed of tracking and precision.〈/p〉 〈p〉The robustness of the networks of neurons opposite the noise of measurements, like, the smoothness of the power signal of PV system generated during the application of the neuronal order, will qualify this command as a practical alternative to the disadvantages recorded on the levels of the classical methods.〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 183〈/p〉 〈p〉Author(s): Sofiane Kichou, Nikolaos Skandalos, Petr Wolf〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉Energy management is very important for the effective operation of a hybrid system composed of various energy sources. The present work aims to develop an effective control strategy in order to reduce the grid-maximal contracted power of a hybrid building containing PV systems, combined heat and power (CHP) unit and battery energy storage system (BESS). The proposed solutions (new control strategy and increased PV system size) were carried out based on the analysis of monitored data collected from May 2016 to April 2017 representing the real behaviour of the hybrid system.〈/p〉 〈p〉The obtained results demonstrated the effectiveness of the developed control strategy in decreasing the grid-maximal contracted power from 140 kW to 120 kW and increasing the self-sufficiency of the building. Furthermore, by combining the proposed control strategy and the proposed PV system, the self-sufficiency can be even more increased and the grid-maximal power can be reduced by 30% leading to an annual savings of almost 4000 €/year.〈/p〉 〈p〉Finally, the financial assessment revealed that the payback period of the proposed solution is less than 10 years confirming the profitability of the investment.〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 183〈/p〉 〈p〉Author(s): Qiang Wang, Kun Luo, Chunlei Wu, Jianren Fan〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The environment-friendly development of wind power is complicated as the atmospheric impacts of wind farms are difficult to measure. Wind power has made contributions to emission reduction, but it is undeniable that the substantial wind farms (SWFs) have had a non-negligible impact on the local ABL. This paper aims to provide a reliable methodological scheme and practical data for human beings to objectively understand the development of wind power. Based on the data from one of the Chinese gigawatt-scale wind power bases in Zhangbei County of Hebei Province, the mesoscale simulations were conducted to explore the impacts of substantial wind farms on the local and regional atmosphere. The results show that: (i) the impact of substantial wind farms on the local area is significant and sustained, while this impact on the regional area is slight and occasional; (ii) it can bring about the seasonal and diurnal differences in the local ABL property; (iii) it can not only induce the horizontal turbulence directly caused by wind turbine wake flow, but also produce the vertical mixing in the near-surface ABL. A systematic analysis of wind power potential and its atmospheric impact is urgent to ensure sustainable development of wind power.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 183〈/p〉 〈p〉Author(s): Hüseyin. Karaca, Cemil Koyunoğlu, Ali Özdemir, Kenan Ergun〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this work, the liquefaction of coal and biomass with direct liquefaction strategy was explored. The point of liquefaction is both to utilize a greater amount of the current coal and biomass assets all the more productively and to create an alternative liquid fuel to oil. Along these lines, the procedure parameters must be resolved to expand the liquefaction efficiency. In addition, it is proposed to do the liquefaction efficiency, particularly in the reactant conditions, to expand the measure of oil. Process parameters were controlled by utilizing Factorial Experimental Design technique in the liquefaction procedures. The solid/liquid ratio was changed as 1/2-1/4, the catalyst concentration was 2–6%, the temperature was 375–400 °C and the duration was 30–90 min. Starting nitrogen pressure was set at 30 bar, stirring speed was 400 rpm, coal/biomass proportion was settled at 1/1. Tetralin as a solvent and MoO〈sub〉3〈/sub〉 as catalyst were utilized. Toward the finish of the liquefaction procedure, the total conversions were computed in view of the acquired non-reactive solid (char). As indicated by the outcomes obtained, the most total conversion (81.9%) was acquired at a solid/liquid proportion of 1/2, a catalyst concentration of 2%, a reaction time of 90 min and a reaction temperature of 400 °C. In light of total conversions and elective liquid fuel (oil) in the given conditions, the solid/liquid ratio should be taken as 1/2, the catalyst concentration is 2%, the reaction time is 30–90 min and the reaction temperature is 400 °C. The lowest reaction time found, in this study, is the innovative solution for reducing co-liquefaction cost preferred.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 187〈/p〉 〈p〉Author(s): Dhivya Sampath Kumar, Anurag Sharma, Dipti Srinivasan, Thomas Reindl〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉With the shift in renewable portfolio standards, conventional fossil-fuel based generators are expected to be partially or fully replaced with renewable energy sources such as photovoltaics (PVs). However, replacing the conventional synchronous generators with PV generators may raise new stability concerns such as lack of inertia, insufficient reactive power and voltage fluctuations, which can jeopardize the reliability of the entire network. In this paper, various impacts of integrating utility-scale PVs and rooftop PVs and replacing the existing conventional generators on the stability of a power network are investigated. Detailed steady state, transient and small signal analyses are conducted on a large test system, namely Texas 2000-bus system for different PV penetration levels. System transients such as line faults, double-line faults, loss of generator, loss of PVs and cloud cover scenarios are simulated to study their impacts on the test system with different PV penetration levels. It is demonstrated from the impact analysis that the benefits of PVs are highly dependent on a spectrum of factors such as node criticality, type, location and penetration of PVs, and type of transients. Furthermore, the influence of battery energy storage system that are generally associated with PVs on the system stability is also discussed.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 187〈/p〉 〈p〉Author(s): Zhengzhi Deng, Chen Wang, Peng Wang, Pablo Higuera, Ruoqian Wang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉As an example of multipurpose utilization of marine structures, the hydrodynamic performance of an offshore-stationary Oscillating Water Column (OWC) device with an immersed horizontal bottom plate was investigated through both experimental tests and numerical simulations. Based on the open source package OpenFOAM and toolbox waves2Foam, the numerical results were validated by comparing them with experimental data. The effects of the opening ratio (〈em〉a〈/em〉), plate length (〈em〉D〈/em〉), relative opening (〈em〉ε〈/em〉), and water depth on the energy absorption efficiency, transmission coefficient, and energy dissipation coefficient were examined over a wide range of wave conditions. The results show that a relatively long bottom plate and small opening ratio is beneficial for both the energy extraction and wave-damping ability, especially for long waves. Increasing the relative vertical opening considerably improves the performance of multipurpose OWC devices. Moreover, the optimal structure configuration is found for parameters 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.svg"〉〈mrow〉〈mi〉a〈/mi〉〈mo linebreak="goodbreak" linebreakstyle="after"〉=〈/mo〉〈mn〉0.65〈/mn〉〈mtext〉%〈/mtext〉〈/mrow〉〈/math〉, 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si2.svg"〉〈mrow〉〈mi〉D〈/mi〉〈mo linebreak="goodbreak" linebreakstyle="after"〉=〈/mo〉〈mn〉2〈/mn〉〈mi〉B〈/mi〉〈/mrow〉〈/math〉 (〈em〉B〈/em〉 is the breadth of chamber), and 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si3.svg"〉〈mrow〉〈mi〉ε〈/mi〉〈mo linebreak="goodbreak" linebreakstyle="after"〉=〈/mo〉〈mn〉1〈/mn〉〈mo linebreak="goodbreak" linebreakstyle="after"〉/〈/mo〉〈mn〉2〈/mn〉〈/mrow〉〈/math〉.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 187〈/p〉 〈p〉Author(s): Hongping Quan, Pengfei Li, Wenmeng Duan, Liao Chen, Langman Xing〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉With the increasing of oil demand and the decreasing of conventional crude oil production, unconventional crude oil is gaining interest. A flow improver (FI) was synthesized and designed a series of methods for investigating the effect of the flow improver on the asphaltene and resin of two unconventional crude oil samples. Changes in the morphology of the solid samples, as determined by scanning electron microscopy. 〈em〉n〈/em〉-Heptane and alcohol were selected as poor solvents for asphaltene and resin, respectively, to prepare solution samples of different concentrations. The precipitation tendency was judged according to the color change of the solution. Fluorescence microscopy was used to observe the changes in the aggregation morphology of the solution samples before and after FI addition. Solid samples and solution samples were tested by XRD and UV spectrophotometry, respectively. The results consistently showed that the effect of FI on resin was better than that on asphaltene. The effect of asphaltene and resin on the viscosity of crude oil was investigated through the series of studies.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 183〈/p〉 〈p〉Author(s): Hongshan Guo, Yongqiang Luo, Forrest Meggers, Marco Simonetti〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We can use the concept of exergy to analyze a human body as a heat emitter: while generating heat continuously, the body remains at roughly the same temperature through physiological responses such as shivering, sweating, breathing thus raising/decreasing the core and/or skin temperature to maintain effective heat dissipation. Existing literature provides an estimated exergy consumption rate of the human body ranging from 2 to 5〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.svg"〉〈mrow〉〈mi〉W〈/mi〉〈mo linebreak="badbreak"〉/〈/mo〉〈msup〉〈mrow〉〈mi〉m〈/mi〉〈/mrow〉〈mrow〉〈mn〉2〈/mn〉〈/mrow〉〈/msup〉〈/mrow〉〈/math〉, while nearly unanimously agreeing on a local exergy consumption minima points to potential individual thermal comfort. To clarify the underlying assumptions used in the existing human body exergy models, we analytically and numerically reviewed the terms used for assessing metabolism, radiation, evaporation, and convection exergy changes of the human body in this paper. We observed overestimations of exergy from metabolism, underestimations of exergy change through radiation, and some caveats in the signage of convective exergy losses in the results we obtained. We were also able to propose an improved expression to estimate human body radiation exergy exchanges as well as selecting reference temperatures that are more process-specific. Future studies that provide experimental verification of these models were also deemed necessary.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 183〈/p〉 〈p〉Author(s): Bin Zou, Yiqiang Jiang, Yang Yao, Hongxing Yang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This work investigated comprehensively the impacts of non-ideal optical factors, including incident angle, sunshape and optical errors on the performance of the parabolic trough collector (PTC). Each optical factor was defined based on their geometrical principles. It was revealed that the heat flux distribution distorted by optical factors was the main cause of changing performance of the PTC. The temperature distribution was completely dependent on the heat flux distribution. The incident angle caused cosine loss and end loss, which respectively reduced the effective incident solar radiation and produced a near-zero heat flux section at one end of the absorber. Based on the effective incident solar radiation, the collector efficiency was reduced by 41.11% with the incident angle increasing from 0° to 60°. Larger circumsolar ratios produced more uniform circumferential temperature distribution, while reduced greatly the collector efficiency. The specularity error and tracking error affected slightly the receiver's safety, while the slope error reduced obviously the threat to the receiver. When specularity error was small enough (〈3 mrad), further improving reflector's specular quality reduced the optical efficiency. The offset direction along X-axis caused the greatest optical loss, and that along positive Y-axis caused local overheating, threatening the receiver's safety.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 183〈/p〉 〈p〉Author(s): Ana Paula Soares Dias, Filipe Rego, Frederico Fonseca, Miguel Casquilho, Fátima Rosa, Abel Rodrigues〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉Poplar biomass of nine different genotypes, from short rotation coppice, was pyrolyzed in a fixed bed reactor using several solid catalysts. Pine bark was used as reference for uncatalyzed pyrolysis. Pyrolysis tests were performed for temperatures in the range 425–500 °C, selected from the thermal degradation profiles obtained by thermogravimetry under N〈sub〉2〈/sub〉 flow. All the analyzed poplar genotypes showed similar pyrolysis behavior, with the highest bio-oil yield (53% average value) being obtained for the highest tested temperature (500 °C). In analogous conditions, the pine bark resulted in higher bio-char yields than poplar biomass, due to its larger lignin content.〈/p〉 〈p〉Catalyzed pyrolysis carried out at 500 °C using 10% of catalyst (W〈sub〉cat〈/sub〉/W〈sub〉biomass〈/sub〉) for H-ZSM5 and FCC (spent catalyst from Fluid Catalytic Cracking unit) zeolites, and Mg and Na carbonates, showed improved gasification with slightly lower liquid production. The FCC catalyst promoted the lowest depreciation of bio-oil yield with the highest decrease of acid functional groups. All the used catalysts were effective to lessen the acidic components of the produced bio-oils thus having a beneficial effect on the pyrolysis liquid products.〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 183〈/p〉 〈p〉Author(s): Wenjun Duan, Yunke Gao, Qingbo Yu, Tianwei Wu, Zhimei Wang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The high quality waste heat recovery of the molten blast furnace slag was necessary and urgent. In this paper, the flow characteristic of the molten slag reactor was investigated by numerical simulation. Firstly, the three-dimensional model was established for investigating the gas-liquid two-phase flow. The gas-liquid flow was modeled to be turbulent, which was described by the RNG 〈em〉k-ε〈/em〉 model, and the interface of gas and liquid was conducted by the VOF model. Secondly, the top-submerged cold experiment system was constructed to validate the accuracy of the simulation model. Thirdly, the bubble behavior, gas phase distribution and molten slag motion were investigated. The bubble in the reactor would go through five stages and the maximum gas fraction reached about 4.87% at 0.75s. Meanwhile, the gas phase distribution and molten slag motion were closely related to the bubble behavior. Ultimately, the matrix analysis method was applied to obtain the optimal parameters of the reactor. The optimal condition improved the flow behavior in the molten BFS reactor significantly. The present results of the simulation provided an insight for the gas-liquid two-phase flow in molten slag reactor, which would provide the theoretical guidance for industrial applications.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 183〈/p〉 〈p〉Author(s): Wu Xiao, Kaifeng Wang, Xiaobin Jiang, Xiangcun Li, Xuemei Wu, Ze Hao, Gaohong He〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A simultaneous optimization approach for heat exchanger network (HEN) synthesis and detailed shell-and-tube heat exchanger (HE) design including phase changes is proposed based on a genetic/simulated annealing algorithm (GA/SA). Firstly, a model for HEN synthesis considering utility HEs with phase change is established by combining the improved stage-wise superstructure model of HEN synthesis with non-isothermal mixing of splits and detailed design models of HEs involving phase change, the minimum total annual cost accounting for pumping cost is set as the key objective. Secondly, two alternative connection schemes for HEs, which are referred to as one-stream series-wound and one-stream parallel in the stage-wise superstructure of the HEN, were applied. Thirdly, a simultaneous optimization strategy is proposed. Required areas of HEs obtained by stage-wise superstructure, overall heat-transfer coefficients and pressure drops based on the dimension parameters of HEs are used to connect HEN synthesis and the detailed design of each HE. Finally, a flowchart of optimization procedures using GA/SA was presented to solve the problem, and an inner iterative loop of the area of HE is used to guarantee the feasibility of the solution. Two examples results are used to illustrate the availability of the proposed model and algorithm.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 183〈/p〉 〈p〉Author(s): Jibin Yang, Xiaohui Xu, Yiqiang Peng, Jiye Zhang, Pengyun Song〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this paper, a tramway's system model is established to evaluate its longitudinal dynamics performance, where the model includes multiple masses point connecting together powered by the catenary and a hybrid energy-storage system which consists of a battery pack and ultracapacitor pack. To explore an optimal or appropriate real-time power distribution among these energy sources, a dual fuzzy logic control-based energy management strategy combined with wavelet transform and multi-objective optimization is proposed. The control parameters of the dual fuzzy logic controller are adjusted using a multi-objective particle swarm optimization algorithm while considering the daily operating cost of the tramway. To verify the effectiveness and validity of the proposed model and energy management strategy, its simulation results are further compared and verified with the field experimental results of a real tramway and a real driving cycle in China.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 183〈/p〉 〈p〉Author(s): Ahmed K. Abbas, Ali A. Bashikh, Hayder Abbas, Haider Q. Mohammed〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉Lost circulation is one of the frequent challenges encountered during the drilling of oil and gas wells. It is detrimental because it can not only increase non-productive time and operational cost but also lead to other safety hazards such as wellbore instability, pipe sticking, and blow out. However, selecting the most effective treatment may still be regarded as an ill-structured issue since it does not have a unique solution. Therefore, the objective of this study is to develop an expert system that can screen drilling operation parameters and drilling fluid characteristics required to diagnose the lost circulation problem correctly and suggest the most appropriate solution for the issue at hand.〈/p〉 〈p〉In the first step, field datasets were collected from 385 wells drilled in Southern Iraq from different fields. Then, 〈em〉f〈/em〉scaret package in R environment was applied to detect the importance and ranking of the input parameters that affect the lost circulation solution. The new models were developed to predict the lost circulation solution for vertical and deviated wells using artificial neural networks (ANNs) and support vector machine (SVM). The using of the machine learning methods could assist the drilling engineer to make an intelligent decision with proper corrective lost circulation treatment.〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 187〈/p〉 〈p〉Author(s): Farzad Jaliliantabar, Barat Ghobadian, Gholamhassan Najafi, Rizalman Mamat, Antonio Paolo Carlucci〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this study an exhaust gas recirculation system was developed for a small single cylinder 4-stroke engine. Then the mathematical models to correlate responses as the engine emissions and performance characteristics to the factors, include engine load, engine speed, EGR rate and biodiesel fuel percent, were developed. Finally, by using the developed models and NSGA-II (Non-dominated Sorting Genetic Algorithm II) method, the factors were optimized. The highest decrease in 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.svg"〉〈mrow〉〈msub〉〈mrow〉〈mtext〉NO〈/mtext〉〈/mrow〉〈mrow〉〈mtext〉x〈/mtext〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉 emissions while using the biodiesel and EGR is 63.76% with B10 fuel blend (10% biodiesel fuel and 90% diesel fuel blend by volume) and 30% EGR rate. The highest reduction in HC emission levels while using EGR and biodiesel simultaneously, has been 54.05%. The adjusted R〈sup〉2〈/sup〉 of the proposed model for the CO, HC, NOx, Power, BSFC and smoke were 0.94, 0.91, 0.88, 0.95, 0.89 and 0.94, respectively. Results of the optimization of the engine factors with NSGA-II method has been satisfactory and the pareto front for different test conditions was proposed. The outcomes of the study revealed that the optimization should be taken into account in the development of the new policy for using of the biofuel in the internal combustion engines.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 187〈/p〉 〈p〉Author(s): Bo Yang, Jingbo Wang, Yiyan Sang, Lei Yu, Hongchun Shu, Shengnan Li, Tingyi He, Lei Yang, Xiaoshun Zhang, Tao Yu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This paper develops a novel passive fractional-order sliding-mode control (PFOSMC) of a supercapacitor energy storage (SCES) system in microgrid with distributed generators. Firstly, a storage function is constructed and thoroughly analysed to investigate the inherent physical characteristics of SCES systems. Then, the beneficial terms are carefully retained for the sake of transient responses improvement, while the other detrimental terms are fully removed to achieve a globally control consistency. In order to further enhance the robustness of the closed-loop system, a fractional-order sliding-mode control (FOSMC) framework is synthesized as an additional input, which employs the fractional-order 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.svg"〉〈mrow〉〈mi mathvariant="bold"〉P〈/mi〉〈msup〉〈mrow〉〈mi mathvariant="bold"〉D〈/mi〉〈/mrow〉〈mrow〉〈mi mathvariant="bold-italic"〉α〈/mi〉〈/mrow〉〈/msup〉〈/mrow〉〈/math〉 sliding surface as well as an energy reshaping mechanism to realize a more flexible control performance. Four case studies, including (a) Active power and reactive power supply, (b) System restoration under power grid fault, (c) Power support under stochastic solar energy and wind energy integration, and (d) Robustness with system parameter uncertainties, are carried out to study the control performance of PFOSMC compared to that of PID control, interconnection and damping assignment passivity-based control (IDA-PBC), and FOSMC, Finally, a hardware-in-the-loop (HIL) experiment using dSpace platform is undertaken to validate its implementation feasibility.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 187〈/p〉 〈p〉Author(s): Anna Crivellari, Valerio Cozzani, Ibrahim Dincer〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In the current context of global energy transition, the coupling of methanol production with offshore oil & gas operations appears to be a promising option to share infrastructures and convert renewable energy into valuable fuel. However, renewable methanol synthesis has not yet reached the commercial stage. Moreover, there is no evidence on studies integrating offshore multiple resources into methanol process. The novelty of this paper is a performance analysis of emerging routes for methanol production driven by offshore wind-solar energies through exergy and exergoeconomic techniques. Two production schemes (catalytic hydrogenation of carbon dioxide and direct radical oxidation of methane) are properly designed to produce a fixed methanol rate driven by offshore wind farm and solar-thermal plants at a given oil & gas rig. The results demonstrate that carbon dioxide-based route shows the lowest exergy destruction rate (66 MW) and total cost rate (1000 $/h) compared to other option. In conjunction with this, the methane-based route gives a satisfactory exergy efficiency of 87% against a mere 2% of other pathway, as well as higher potential to increase cost savings due to lower exergoeconomic factor. Furthermore, influences of varying some key variables on the proposed parameters of the two options are investigated.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 187〈/p〉 〈p〉Author(s): Peng Jiang, Ashak Mahmud Parvez, Yang Meng, Meng-xia Xu, Tian-chi Shui, Cheng-gong Sun, Tao Wu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The indirect steam gasification of biomass to olefins (IDBTO) coupled with CO〈sub〉2〈/sub〉 utilization was proposed and simulated. Energy and exergy efficiencies, net CO〈sub〉2〈/sub〉 emissions, and economic evaluation were performed against IDBTO as well as the direct oxygen-steam gasification of biomass to olifins (DBTO). The influences of unreacted gas recycling fraction (RU) and CO〈sub〉2〈/sub〉 to dry biomass mass ratio (CO〈sub〉2〈/sub〉/B) on the thermodynamic performance of the processes were also studied. The results showed that the yields of olefins of DBTO and IDBTO were 17 wt% and 19 wt%, respectively, the overall energy and exergy efficiencies of the IDBTO were around 49% and 44%, which were 8% and 7% higher than those of the DBTO process, respectively. A higher RU was found favor higher energy and exergy efficiencies for both routes. Besides, for the IDBTO process, it is found that the addition of CO〈sub〉2〈/sub〉 to gasification system led to an improvement in both energy efficiency and exergy efficiency by around 1.6%. Moreover, life-cycle net CO〈sub〉2〈/sub〉 emission was predicted to be −4.4 kg CO〈sub〉2〈/sub〉 eq./kg olefins for IDBTO, while for DBTO, it was −8.7 kg CO〈sub〉2〈/sub〉 eq./kg. However, the quantitative economic performance of IDBTO was superior to that of the DBTO process.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 187〈/p〉 〈p〉Author(s): Kevin S. Kung, Ahmed F. Ghoniem〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Drying is a crucial process in many thermochemical processes for bioenergy. However, most existing drying models often have the following shortcomings: they are feedstock-dependent, or they are unable to describe the spatial inhomogeneity that often develops within thermally thick biomass particles under higher temperature gradients. In this paper, a multi-scale analysis was undertaken on the dynamics of drying thermally thick biomass under high temperatures, based on a new physical drying kinetics approach that is independent on feedstock-specific empirical parameters. A single-particle approach was then layered onto this kinetics model to understand how the spatially inhomogeneous moisture and temperature profiles inside a biomass particle evolve over time during drying. This process generates predicted temperature and drying time profiles that were successfully validated against experimental data. Subsequently, the impact on drying by various factors—particle size, geometry, initial moisture content, and reactor temperature—was studied. These observations were used to consider the design choices of a commercial-scale dryer, highlighting the key trade-offs, as well as optimized combinations of temperature and particle size that minimizes the operating cost. The approach described in this paper can be readily integrated into other mathematical descriptions of bioenergy conversion processes such as gasification and combustion.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 187〈/p〉 〈p〉Author(s): Tim Conroy, Maurice N. Collins, Ronan Grimes〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A variety of tube materials and geometries are considered in an analysis that identifies suitable sodium receiver designs for integration with next-generation thermodynamic power cycles. Sodium is capable of delivering outlet temperatures of 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.svg"〉〈mrow〉〈mo〉〉〈/mo〉〈msup〉〈mrow〉〈mn〉750〈/mn〉〈/mrow〉〈mrow〉〈mo〉∘〈/mo〉〈/mrow〉〈/msup〉〈mi〉C〈/mi〉〈/mrow〉〈/math〉, however the net power output diminishes with rising temperatures due to tube material limitations on allowable flux density and increasing heat losses. Small tube diameters facilitate large thermal efficiencies and heat fluxes for all materials, however a large pressure drop penalty can somewhat mitigate these advantages. Traditional heat exchanger alloys perform quite poorly in comparison to Inconel 617 and Haynes 230, with allowable heat flux decreasing significantly as temperatures are increased beyond 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si2.svg"〉〈mrow〉〈msup〉〈mrow〉〈mn〉600〈/mn〉〈/mrow〉〈mrow〉〈mo〉∘〈/mo〉〈/mrow〉〈/msup〉〈mi〉C〈/mi〉〈/mrow〉〈/math〉. Multi-pass concepts offer greater control of flow-path exposure to the heat flux boundary condition than straightforward single-pass designs. A triple-panel design with small diameter Inconel 617 tubes balances thermal, hydraulic, and mechanical performance most effectively across all temperatures. For all candidate materials, sodium can augment power plant efficiency when integrated with a high temperature cycle (〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si3.svg"〉〈mrow〉〈mo〉〉〈/mo〉〈msup〉〈mrow〉〈mn〉600〈/mn〉〈/mrow〉〈mrow〉〈mo〉∘〈/mo〉〈/mrow〉〈/msup〉〈mi〉C〈/mi〉〈/mrow〉〈/math〉). A combined receiver and power cycle efficiency percentage point improvement of 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si4.svg"〉〈mrow〉〈mn〉1.5〈/mn〉〈mtext〉%〈/mtext〉〈/mrow〉〈/math〉 is possible using 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si5.svg"〉〈mrow〉〈mi〉N〈/mi〉〈mi〉i〈/mi〉〈/mrow〉〈/math〉-based superalloys at 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si6.svg"〉〈mrow〉〈mo〉∼〈/mo〉〈mn〉650〈/mn〉〈mo linebreak="goodbreak" linebreakstyle="after"〉−〈/mo〉〈msup〉〈mrow〉〈mn〉700〈/mn〉〈/mrow〉〈mrow〉〈mo〉∘〈/mo〉〈/mrow〉〈/msup〉〈mi〉C〈/mi〉〈/mrow〉〈/math〉 compared to a baseline outlet temperature of 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si7.svg"〉〈mrow〉〈msup〉〈mrow〉〈mn〉550〈/mn〉〈/mrow〉〈mrow〉〈mo〉∘〈/mo〉〈/mrow〉〈/msup〉〈mi〉C〈/mi〉〈/mrow〉〈/math〉, resulting in a solar-to-electric power output increase of over 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si8.svg"〉〈mrow〉〈mn〉4〈/mn〉〈mtext〉%〈/mtext〉〈/mrow〉〈/math〉.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 187〈/p〉 〈p〉Author(s): Nor Erniza Mohammad Rozali, Wai Shin Ho, Sharifah Rafidah Wan Alwi, Zainuddin Abdul Manan, Jiří Jaromír Klemeš, Jing Shenn Cheong〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The hybrid power system (HPS) that integrates diesel/biodiesel plant with renewable energy (RE) technologies has become increasingly popular to alleviate greenhouse gases emissions issue of the sole diesel/biodiesel power system. Integrated diesel-RE power system offers cleaner power supply while minimising cost of diesel fuel and diesel system maintenance. The use of Power Pinch Analysis (PoPA) method for the integration of diesel plants and RE systems into HPS with the objective to minimise fuel requirement and operational time of diesel generator has been presented. This work aims to achieve the same objective via probability theory utilisation, to simplify the PoPA procedure involving the matching of various routes for power flows. The extended technique called the Probability-Power Pinch Analysis (P-PoPA) can give accurate results as those established from the PoPA method within a shorter analysis time because it replaces the tedious manual matching step with correction factors. All probable routes of power from RE and diesel generators to demands are considered in computing the correction factors, in order to target the minimum diesel power in the integrated system. The result of a Case Study demonstrates that 19% saving in diesel fuel consumption can be realised if the present diesel station is supported with renewable solar power in an HPS. The result of the P-PoPA method is accurate with a very minor deviation to that from the conventional PoPA technique.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 187〈/p〉 〈p〉Author(s): Monaaf D.A. Al-Falahi, Shantha D.G. Jayasinghe, Hossein Enshaei〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The move towards electrification of marine vessels enables the development of more efficient vessels by reducing fuel consumption and emissions. This includes incorporating electrical energy sources, storage systems and interfacing power electronic converters which increase system complexity. Therefore, an accurate and efficient power management system (PMS) is essential to achieve the optimum operation. This study aims to develop a novel hybrid meta-heuristic algorithm-based PMS for the fuel savings of hybrid electric ferries. The ferry power system used in this study comprises two diesel generator sets and a battery storage system. The proposed hybrid PMS method applies an interactive approach on the basis of a grey wolf optimizer (GWO) and fuzzy expert system to improve the computational efficiency of the algorithm. Measured load data from an existing short-haul ferry are used in the simulation under two load scenarios: normal and high load demands. The proposed fuzzy logic-grey wolf optimizer (FL-GWO) aims to minimize the operating cost of the proposed system while satisfying all operational and technical constraints of the ferry. Results show that the proposed FL-GWO provided a more accurate optimal solution set with less standard deviation than the GWO. The proposed method realized up to 3.14% and 1.81% fuel savings in normal- and high-load scenarios, respectively, compared with GWO. Moreover, the sensitivity analysis indicates that charging the battery from the onboard generators in a more uniform rate over the entire cruising period reduces the fuel consumption.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S036054421931607X-egi10JVZ5T057D.jpg" width="278" alt="Image 105057" title="Image 105057"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 187〈/p〉 〈p〉Author(s): Michael Tang, Jia-Cheng Chang, S. Rajesh Kumar, Shingjiang Jessie Lue〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this work, the effect of electrolyte composition was evaluated on lithium-oxygen (Li–O〈sub〉2〈/sub〉) battery using carbon cloth air electrode. Seven ether-based solvents were measured for their conductivity, viscosity, contact angle and decomposition temperature. The results were compiled with other physical properties to screen potential solvents for future testing. Diglyme and tetraglyme were identified and each of them was individually mixed with one of four lithium salts, yielding eight combinations of electrolytes. These electrolytes were assembled into Li–O〈sub〉2〈/sub〉 batteries and the voltage and capacity data were recorded during cycling discharge/charge test. The effects of organic electrolyte physical properties on the battery impedance and cyclic life were discussed. Among the eight electrolytes, lithium bis(trifluoromethane) sulfonimide (LiTFSI) in tetraethylene glycol dimethyl ether (tetraglyme) resulted in the longest cyclic life at a discharge capacity cutoff of 2000 mAh g〈sub〉Pt〈/sub〉〈sup〉−1〈/sup〉 than other compositions. This performance may be ascribed to the electrolyte's high conductivity, sufficient viscosity and suitable contact angle with the air electrode.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 187〈/p〉 〈p〉Author(s): Alain Ulazia, Jon Sáenz, Gabriel Ibarra-Berastegi, Santos J. González-Rojí, Sheila Carreno-Madinabeitia〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The literature typically considers constant annual average air density when computing the wind energy potential of a given location. In this work, the recent reanalysis ERA5 is used to obtain global seasonal estimates of wind energy production that include seasonally varying air density. Thus, errors due to the use of a constant air density are quantified. First, seasonal air density changes are studied at the global scale. Then, wind power density errors due to seasonal air density changes are computed. Finally, winter and summer energy production errors due to neglecting the changes in air density are computed by implementing the power curve of the National Renewable Energy Laboratorys 5 MW turbine. Results show relevant deviations for three variables (air density, wind power density, and energy production), mainly in the middle-high latitudes (Hudson Bay, Siberia, Patagonia, Australia, etc.). Locations with variations from −6% to 6% are identified from summers to winters in the Northern Hemisphere. Additionally, simulations with the aeroelastic code FAST for the studied turbine show that instantaneous power production can be affected by greater than 20% below the rated wind speed if a day with realistically high or low air density values is compared for the same turbulent wind speed.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 187〈/p〉 〈p〉Author(s): Jianghui Luo, Chun Zou, Yizhuo He, Huixiang Jing, Sizhe Cheng〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The characteristics and mechanism of NO formation during pyridine oxidation in O〈sub〉2〈/sub〉/CO〈sub〉2〈/sub〉 atmospheres are investigated both experimentally and numerically. Comparison experiments in O〈sub〉2〈/sub〉/N〈sub〉2〈/sub〉 and O〈sub〉2〈/sub〉/CO〈sub〉2〈/sub〉 atmospheres are performed in a flow reactor at atmospheric pressure covering fuel-rich to fuel-lean equivalence ratios with temperature ranging from 773 K to 1573 K. Experimental results indicated that HCN is completely consumed in CO〈sub〉2〈/sub〉 atmospheres, whereas significant amounts remain in N〈sub〉2〈/sub〉 atmospheres under fuel-rich conditions. Compared with O〈sub〉2〈/sub〉/N〈sub〉2〈/sub〉 atmospheres, the formation of NO in O〈sub〉2〈/sub〉/CO〈sub〉2〈/sub〉 atmospheres is reduced by 8.85% and 5.8% under stoichiometric and fuel-lean conditions respectively, whereas it is 5.15% greater under fuel-rich conditions. A newly developed chemical kinetic mechanism based on our previous studies satisfactorily reproduced the main features of CO, HCN, and NO formation. The conversion differences of pyridine to NO between O〈sub〉2〈/sub〉/CO〈sub〉2〈/sub〉 and O〈sub〉2〈/sub〉/N〈sub〉2〈/sub〉 atmospheres are mainly due to the differences of conversion of HCN to NO. The conversion ratio discrepancies of pyridine to HCN are all less than 2%. The conversion ratios of HCN to NO in O〈sub〉2〈/sub〉/N〈sub〉2〈/sub〉 and O〈sub〉2〈/sub〉/CO〈sub〉2〈/sub〉 atmospheres are 7.2% and 15.6% under fuel-rich conditions, 65.3% and 57.4% under stoichiometric conditions, and 83.5% and 76.3% under fuel-lean conditions, respectively.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 187〈/p〉 〈p〉Author(s): Mohammad H. Shams, Majid Shahabi, Mohsen Kia, Alireza Heidari, Mohamed Lotfi, Miadreza Shafie-khah, João P.S. Catalão〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Microgrids are often designed as energy systems that supply electrical and thermal loads with local resources such as combined heat and power units, renewable energy sources, diesel generators, and others. However, increasing interaction between natural gas and electrical systems, in addition to increased penetration of natural gas fired units gives rise to both opportunities and challenges in microgrid operation scheduling. In this paper, the energy hub concept is used to construct a scenario-based model for the optimal scheduling of electrical and thermal resources in a microgrid with integrated electrical and natural gas infrastructures. The objective function of the proposed model minimizes the expected operation costs while considering all network constraints and uncertainties. The natural gas and electricity flow equations are linearized and formulated as a mixed-integer linear programming problem. Scenarios associated with stochastic variables such as renewable generation and electrical and thermal loads are generated using the corresponding probability distribution functions and reduced using a scenario reduction technique. The proposed model is applied to an energy hub-based microgrid and the simulation results demonstrate the effectiveness of the approach. Furthermore, the benefits of implementing electrical and thermal demand response schemes are quantified. Also, more in-depth analyses for this network-constrained model are performed, including natural gas flow rate variations, natural gas pressures, power flow, and nodal voltages.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 187〈/p〉 〈p〉Author(s): Mingzhang Pan, Zeyuan Zheng, Rong Huang, Xiaorong Zhou, Haozhong Huang, Jiaying Pan, Zhaohui Chen〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉n-Octanol with its high energy density and high cetane number has similar fuel properties as diesel fuel, and is thus considered an excellent choice for alcohol fuels as a substitute for diesel. This study focused on the effects of exhaust gas recirculation (EGR) combined with the addition of n-octanol on the performance, emissions, and particulate matter (PM) of a direct injection diesel engine. The results show that the curves of the in-cylinder pressure of n-octanol/diesel blends nearly overlap those of pure diesel fuel under the test conditions. At a low EGR ratio, the brake thermal efficiency of n-octanol/diesel blends is higher than that of diesel fuel. With an increase in the EGR ratio, the results show that nitrogen oxide (NO〈sub〉X〈/sub〉) emissions decrease, whereas carbon monoxide (CO) and soot emissions significantly increase. However, the use of n-octanol/diesel blends can inhibit the increase in CO and soot emissions appreciably. In addition, with an increase in n-octanol content in the blends, the number concentration of particles on the particle size distribution decreases gradually. To summarize, a simultaneous reduction in NO〈sub〉X〈/sub〉 and PM emissions under a combined operation of small EGR ratios and n-octanol blends can be realized, thereby improving the brake thermal efficiency.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 187〈/p〉 〈p〉Author(s): Junyoung Park, Jinkyoo Park〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We propose a physics-inspired data-driven model that can estimate the power outputs of all wind turbines in any layout under any wind conditions. The proposed model comprises two parts: (1) representing a wind farm configuration with the current wind conditions as a graph, and (2) processing the graph input and estimating power outputs of all the wind turbines using a physics-induced graph neural network (PGNN). By utilizing the form of an engineering wake interaction model as a basis function, PGNN effectively imposes physics-induced bias for modelling the interaction among wind turbines into the network structure. simulation study shows that the combination of a graph representation of a wind farm and PGNN produce not only accurate and generalizable estimations but also physically explainable estimations. That is, the computing and reasoning procedures of PGNN can be understood by analyzing the intermediate features of the model. We also conduct a layout optimization experiment to show the effectiveness of PGNN as a differentiable surrogate model for wind farm power estimations.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 187〈/p〉 〈p〉Author(s): Andrés Z. Mendiburu, Aguinaldo M. Serra, José C. Andrade, Lucas M. Silva, José C. Santos, João A. de Carvalho〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉Ethanol–air deflagrations were experimentally studied inside a closed tube by varying the equivalence ratio (0.9–1.4) and the initial pressure (20–60 kPa). The flame front inversion phenomenon was observed in all tests. It was determined that the ratio of the distance of flat flame formation to the hydraulic diameter 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.svg"〉〈mrow〉〈mrow〉〈mo stretchy="true"〉(〈/mo〉〈mrow〉〈msub〉〈mrow〉〈mi〉d〈/mi〉〈/mrow〉〈mrow〉〈mi〉f〈/mi〉〈/mrow〉〈/msub〉〈mo〉/〈/mo〉〈msub〉〈mrow〉〈mi〉d〈/mi〉〈/mrow〉〈mrow〉〈mi〉h〈/mi〉〈/mrow〉〈/msub〉〈/mrow〉〈mo stretchy="true"〉)〈/mo〉〈/mrow〉〈/mrow〉〈/math〉 is a measurable parameter that allows the characterization of the phenomenon.〈/p〉 〈p〉For ethanol–air mixtures two dimensionless parameters can be used to correlate 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si2.svg"〉〈mrow〉〈msub〉〈mrow〉〈mi〉d〈/mi〉〈/mrow〉〈mrow〉〈mi〉f〈/mi〉〈/mrow〉〈/msub〉〈mo linebreak="badbreak"〉/〈/mo〉〈msub〉〈mrow〉〈mi〉d〈/mi〉〈/mrow〉〈mrow〉〈mi〉h〈/mi〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉, namely, the ratio of the laminar flame speed to the speed of sound of the reactants 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si3.svg"〉〈mrow〉〈mrow〉〈mo stretchy="true"〉(〈/mo〉〈mrow〉〈msub〉〈mrow〉〈mi〉S〈/mi〉〈/mrow〉〈mrow〉〈mi〉L〈/mi〉〈/mrow〉〈/msub〉〈mo〉/〈/mo〉〈msub〉〈mrow〉〈mi〉C〈/mi〉〈/mrow〉〈mrow〉〈mi〉S〈/mi〉〈mo〉,〈/mo〉〈mn〉0〈/mn〉〈/mrow〉〈/msub〉〈/mrow〉〈mo stretchy="true"〉)〈/mo〉〈/mrow〉〈/mrow〉〈/math〉 and the dimensionless distance travelled by the flame tip up to the time when the flame touches the lateral walls of the tube 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si4.svg"〉〈mrow〉〈mrow〉〈mo stretchy="true"〉(〈/mo〉〈mrow〉〈msub〉〈mrow〉〈mi〉ξ〈/mi〉〈/mrow〉〈mrow〉〈mi〉t〈/mi〉〈mi〉i〈/mi〉〈mi〉p〈/mi〉〈mo〉,〈/mo〉〈mi〉w〈/mi〉〈mi〉a〈/mi〉〈mi〉l〈/mi〉〈mi〉l〈/mi〉〈/mrow〉〈/msub〉〈/mrow〉〈mo stretchy="true"〉)〈/mo〉〈/mrow〉〈/mrow〉〈/math〉. Two correlations were obtained and the averages of the absolute values of the relative errors (AARE) were less than 1.2%. Another correlation was obtained considering published data of different fuel–air mixtures. A statistical analysis applied considering experimental data from published literature and from this work, showed an AARE of 8.95% and a coefficient of multiple determination (R〈sup〉2〈/sup〉) of 0.79. The p-values of the regression coefficients were lower than 0.001. Therefore, the correlations present good accuracy and can be used for prediction.〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 187〈/p〉 〈p〉Author(s): Venkatesh Paramesh, Vadivel Arunachalam, Arun Jyoti Nath〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The present study was undertaken to explore the impact of no nutrient, organic nutrition, and integrated nutrient management on ecosystem services, and the energy balance of the arecanut based intercropping system. Most indicators of ecosystem services were influenced significantly by nutrient management practices. The energy efficiency (1.72) and net energy (19625 MJ ha〈sup〉−1〈/sup〉) improved significantly in the organic nutrient practice due to lower energy input (30722 MJ ha〈sup〉−1〈/sup〉) and higher energy output (50347 MJ ha〈sup〉−1〈/sup〉). The mean values of the indicator of dependence on non-renewable energy sources and an indicator of farm autonomy for organic farms were 0.3 and 0.46, respectively. The study suggests 46% of the inputs produced in the farm were recycled in the organic farms. The significantly higher sustainability yield index (0.25), sustainability value index (0.44) and system economic efficiency (21 USD day〈sup〉−1〈/sup〉) were observed in the organic nutrient system. The study concludes that organic nutrition along with adequate management is required to harness the potential of arecanut based cropping system to improve energy efficiency, ecosystem services, and soil quality to achieve sustainability.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 187〈/p〉 〈p〉Author(s): Hueon Namkung, Young-Joo Lee, Ju-Hyoung Park, Gyu-Seob Song, Jong Won Choi, Joeng-Geun Kim, Se-Joon Park, Joo Chang Park, Hyung-Taek Kim, Young-Chan Choi〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Partially melted ash particles cause increased ash fouling, agglomeration and sintering behaviors during biomass combustion. In addition, ash fouling facilitates the corrosion behavior of stainless steel. In this work, the agglomeration/sintering and corrosion behaviors of untreated herbaceous biomass ash and that pre-treated by an alkali metal leaching reaction were investigated under combustion conditions. Although the ash agglomeration tendency increased with increasing temperature, the tendency was reduced by alkali metal leaching pre-treatment. During comparison of sintering behavior, the degree of sintering (〈em〉x/r〈/em〉) increased as a function of time but was substantially alleviated by alkali metal leaching pre-treatment. In comparison to the typical Frenkel sintering model, a modified Frenkel sintering model was shown to fit well with the experimental sintering behavior. Alkali metal leaching pre-treatment inhibited ash particle adhesion and made high melting temperature minerals, which was verified by scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX), X-ray diffraction (XRD) analysis, the use of ternary mineral phase diagrams and adoption of a new chemical classification system. Furthermore, from SEM-EDX, alkali metal leaching pre-treatment was seen to reduce the corrosion by ash fouling on stainless steel (SUS) 316. Resultingly, the alkali metal leaching pre-treatment significantly alleviated the ash adhesion and corrosion behaviors.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 186〈/p〉 〈p〉Author(s): Zhao-bo Du, Wei Huang, Li Yan〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The fuel-air mixing process plays an important role in the shock-induced combustion ramjet (shcramjet) engine. In the current study, the investigation of front fuel jet and rear air jet is provided in order to study the mixing effect induced by the air jet and reveal the mixing augmentation mechanism and formation of several recirculation zones. Some parameters are also provided to evaluate the flow field properties quantitatively, namely the mixing efficiency, the total pressure recovery coefficient, the fuel penetration depth and the mixing length. The obtained results predicted by the three-dimensional Reynolds-average Navier-Stokes (RANS) equations coupled with the two equation shear stress transport (SST) k-ω turbulence model show that the additional air jet is really beneficial for accelerating the mixing process and improving the mixing efficiency. The shear vortex and air injected are the key sources for the mixing enhancement mechanism of the dual injection strategy. The formations of recirculation zones midstream and downstream are provided as well. The midstream recirculation zone “R〈sub〉2〈/sub〉” is related to both front fuel jet and rear air jet, and “R〈sub〉3〈/sub〉” is related to the air jet only. The downstream recirculation zone1 is composed by flows from the fuel jet and the air jet, and the downstream recirculation zone2 is formed by hydrogen flows.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 186〈/p〉 〈p〉Author(s): Guangming Chen, Volodymyr Ierin, Oleksii Volovyk, Kostyantyn Shestopalov〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The paper presents the results of thermodynamic analysis of ejector cooling cycles with heat pumping devices which supply the working fluid to the vapor generator. Two variants of heat pumping devices are considered in which the feed pump is driven by (1) an expander and a turbine and (2) a turbine. A mathematical model for determining the energy and exergy characteristics of the pumping devices and ejector systems as a whole is proposed. Refrigerant R245ca is selected as an environmentally friendly low-boiling working fluid of the ejector cooling cycles. The paper analyzes the effect of condensing and generating temperatures on the characteristics of ejector cooling cycles for the air conditioning systems. It is shown that the use of the work obtained in the expander and turbine taking into account the irreversibility of the working processes in the pumping devices leads to a slight decrease in the energy efficiency of the proposed systems, and, at the same time, it significantly increases their exergic efficiency.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 186〈/p〉 〈p〉Author(s): F.M. Andersen, G. Henningsen, N.F. Møller, H.V. Larsen〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉To assess future challenges for the energy system, the transmission - and distribution grids, long-term projections of the spatial distribution of electricity consumption with an hourly resolution is important. Based on 2015 data from hourly meters in Denmark, we develop a model that converts national projections of the annual electricity consumption to projections of the hourly consumption in Danish municipalities. Due to different weights and consumption profiles for categories of customers, both the level and the hourly consumption profile differ between municipalities; also future changes will differ.〈/p〉 〈p〉To illustrate future changes, the latest official projection by the Danish Transmission System Operator is used, showing a moderate increase in classic consumption and a considerable increase in total consumption due to electrification of the heating and transport sectors. In addition, the projection includes a number of large datacentres. Electric vehicles and individual heat pumps will determine the future consumption profile in municipalities, while large datacentres mainly determine the level of consumption at specific nodes in the grid. That is, electric vehicles and heat pumps challenge both the energy system, the transmission and the local distribution grids, while large datacentres mainly challenge the energy system and specific nodes in the overall transmission grid.〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 186〈/p〉 〈p〉Author(s): Jin-hua Huo, Zhi-gang Peng, Kun Xu, Qian Feng, De-yang Xu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The lower heat of hydration and temperature rise of slurry were required for hydrates formation cementing, the traditional experimental methods often result in a great reducing in the application performances. Therefore, the organic and inorganic composites were applied to develop a novel cement slurry, which could be used for hydrates layer in deep-water region or permafrost. Firstly, the micro-encapsulated phase change materials (MPCM) containing low melting point paraffin wax with urea formaldehyde resin shell was prepared by the method of in situ polymerization, the basic performances of MPCM, such as chemical structure, encapsulation rate and phase change properties, were studied. Secondly, the slag and fly ash were firstly added into class G oil well cement to reduced the heat of hydration and temperature profiles through chemical means. Then, the MPCM was added and applied to control the heat evolution and regulate temperature profiles, and a novel micro-encapsulated phase change materials with low melting point slurry was provided. Based on above study, a low temperature profiles and hydration heat cement slurry was developed by using organic and inorganic composites, and the developed slurry could be well applied in deep-water region or permafrost cementing to prevent the destabilization of hydrates.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 186〈/p〉 〈p〉Author(s): Wei Chen, Yunfeng Yang, Tengxi Wang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Gas adsorption/desorption and non-linear mass transport in ultra-tight shale were very sensitive to temperature and they become even more intricate as temperature changed. In this study, a self-similarity mathematical model was developed to simulate the gas decline process under 〈strong〉t〈/strong〉hermal stimulation conditions. This model not only incorporated slip and free molecular flow but also gas adsorption/desorption. Besides, a canister test was conducted to study the effect of heating temperature on gas production rates of a fresh shale core. The experiment results showed that gas production rate was increased by raising the heating temperature. Free gas is the main source for the gas flow under 55 °C, while adsorbed gas is the main source under 110 °C. Lastly, the declined trend of simulated gas production rate followed a power law of 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.svg"〉〈mrow〉〈msup〉〈mrow〉〈mi〉t〈/mi〉〈/mrow〉〈mrow〉〈mo〉−〈/mo〉〈mn〉0.509〈/mn〉〈/mrow〉〈/msup〉〈mo linebreak="goodbreak" linebreakstyle="after"〉+〈/mo〉〈msup〉〈mrow〉〈mi〉t〈/mi〉〈/mrow〉〈mrow〉〈mo〉−〈/mo〉〈mn〉0.736〈/mn〉〈/mrow〉〈/msup〉〈/mrow〉〈/math〉 at 55 °C and 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si2.svg"〉〈mrow〉〈msup〉〈mrow〉〈mi〉t〈/mi〉〈/mrow〉〈mrow〉〈mo〉−〈/mo〉〈mn〉0.169〈/mn〉〈/mrow〉〈/msup〉〈mo linebreak="goodbreak" linebreakstyle="after"〉+〈/mo〉〈msup〉〈mrow〉〈mi〉t〈/mi〉〈/mrow〉〈mrow〉〈mo〉−〈/mo〉〈mn〉1.828〈/mn〉〈/mrow〉〈/msup〉〈/mrow〉〈/math〉 under at 110 °C, which matched the experimental data well. From the scaling data, it was suggested that free molecular diffusion was the main gas transport form inside the shale both under 55 °C–110 °C. Our experimental results and theoretic model showed that higher heating temperature could promote the gas production rate significantly, and the model can well predict the non-linear gas transport process.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 186〈/p〉 〈p〉Author(s): Yafei Li, Jianqiang Deng, Li Ma〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This paper presented an experimental study to explore the primary flow expansion characteristics in the transcritical CO〈sub〉2〈/sub〉 two-phase ejectors for various primary nozzle diverging angles (NDAs) and secondary flow pressure. The phase change of the primary flow was visualized, and the effect of the primary flow expansion state on the entrainment ratio was evaluated. The results disclosed that the primary flow changed from the under-expanded state to the over-expanded state with increasing the NDA, and the primary flow expansion state was insensitive to the secondary flow pressure. The visualization images showed that the phase change position moved towards the nozzle exit visibly when the NDA was 0.0°, and the effect of secondary flow pressure on the phase change position was insignificant. Besides, the results revealed that the over-expanded state of primary flow had a negative effect on the entrainment ratio, and the entrainment ratio obtained the maximum when the NDA was 2.0°. The present work is indispensable to realize a comprehensive understanding of the primary flow expansion mechanism inside the transcritical CO〈sub〉2〈/sub〉 ejector, and the insights gained from this study may be of assistance to optimize the ejector structure and improve the ejector performance.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 186〈/p〉 〈p〉Author(s): I. Hernández-Pérez, I. Zavala-Guillén, J. Xamán, J.M. Belman-Flores, E.V. Macias-Melo, K.M. Aguilar-Castro〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In Mexico, the owners of homes use roof coating materials for waterproofing purposes and usually select them just for aesthetic reasons. In this work, four concrete roofs with different waterproofing materials (terracotta, white, gray, and black) were tested under weather conditions of Cuernavaca, Mexico. A set-up with two outdoor test boxes in which the roofs can be exchanged was monitored for six weeks of spring 2015. Three comparative tests (terracotta-black, white-black, and gray-black) were carried out during the period with the highest solar radiation of the year. The results showed that the white roof (WR) had the best thermal performance, under peak solar irradiance it was 29 °C cooler than the black roof (BR) and just 1.5 °C hotter than the outdoor air. Moreover, the average daily energy gain of the WR was 73% smaller than the BR. The terracotta roof (TR) and the gray roof (GR) had peak temperatures of 10 and 14 °C lower than the BR. Moreover, the TR and the GR had daily energy gains 33 and 38% smaller than the BR, respectively, but they are significant compared to one of the WR. Therefore, white waterproofing materials for roofs should be used in Mexico as a passive cooling strategy to prevent solar energy gains of buildings.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 186〈/p〉 〈p〉Author(s): Ali Mohammadi〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Given the structural limitations of ejectors, in order to enhance the flexibility of them to suit various industries, several ejectors may be connected to each other serially. Moreover, steam ejectors are employed in different applications to draw air. In this study, through the agency of computational fluid dynamics, the geometric parameters of multi-stage steam ejectors for air suction were examined, the result of which was validated against experimental data. In this regard, considering an ejector with two stages, attempts were made to investigate the effects of geometric parameters including the diameters of the nozzle, the mixing chamber, the throat, and nozzle exit position (NXP) for either ejector. Accordingly, having evaluated the effects of the mentioned parameters, the most suitable values were selected to satisfy not only the proper functioning of each stage but the entrainment and compression ratio as well. The compression ratios obtained for the first and the second stages are 4.25 and 2.875, respectively which gives rise to a compression ratio of 12.219 for the multi-stage ejector. Eventually, for the final geometry of the ejectors, the Mach number, as well as pressure contour, were demonstrated and analyzed.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 186〈/p〉 〈p〉Author(s): Fatemeh Mostashari-Rad, Ashkan Nabavi-Pelesaraei, Farshad Soheilifard, Fatemeh Hosseini-Fashami, Kwok-wing Chau〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The objective of this study is to comprehensively optimize energy usage and determine mitigation of greenhouse gas (GHG) emissions in agricultural and horticultural crops of Guilan Province, Iran. For this purpose, required data are collected from eggplant, garlic, tea, hazelnut, kiwifruit and tangerine producers through questionnaires. In this study, GHG emissions are investigated under both On-Farm and Off-Farm sectors. Data envelopment analysis method is employed for the optimization of GHG emissions and energy flow. The highest and lowest energy consumption are related to tea and kiwifruit production, respectively. Results show that kiwifruit and eggplant have the highest scores in technical efficiency whilst tangerine and tea have the highest values in pure technical efficiency. The largest amount of energy is saved in kiwifruit orchards with 8316.29 MJ ha〈sup〉−1〈/sup〉. Nitrogen fertilizer and diesel fuel have the topmost energy saving potential in most crops. Kiwifruit orchards have the highest potential for mitigation of GHG gas emissions (520.79 kg CO〈sub〉2 eq〈/sub〉. ha〈sup〉−1〈/sup〉). Results show that an appropriate usage of nitrogen fertilizer and replacement by organic fertilizer will mitigate GHG emissions as well as energy consumption. It can be concluded that GHG emissions can be mitigated by energy optimization in all the studied crops.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 186〈/p〉 〈p〉Author(s): Ali Edalati-nejad, Sayyed Aboozar Fanaee, Javad Khadem〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this paper, the time dependent study of methane-air premixed counterflow flame into a newly proposed plus-shaped channel, in order to obtain effects of palladium catalyst surfaces on the flame structure and pollutant emissions, is described. The results are presented at non-catalytic and catalytic conditions with considering effects of reaction time and various equivalence ratios, from lean to rich combustion, on flame characteristics and pollutant emissions. The governing equations are composed of continuity, momentum, energy and mass fraction equations are numerically solved considering a coupled Piso scheme and Simple algorithm. The comparison between the presented model and published data shows an acceptable agreement that confirms the accuracy of this solution. The average values of CH〈sub〉4〈/sub〉 mass fraction over the geometry at the presence of palladium catalyst is nearly decreased 25% relative to non-catalytic case. The existence of Palladium catalyst has great impact, mostly 34% decrease, on CO formation but the catalyst leads to increment of CO〈sub〉2〈/sub〉 formation 5%. At different values of equivalence ratio, the average temperature of non-catalytic flame is about 16% lower than catalytic one.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 186〈/p〉 〈p〉Author(s): Andra Blumberga, Ritvars Freimanis, Indra Muizniece, Kriss Spalvins, Dagnija Blumberga〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Today buildings become part of Smart Energy Systems. 4th generation district heating network requires buildings with low energy consumption. In Europe, historic buildings account for around 30% from total buildings stock with high energy consumption which has to be reduced. Many of them have heritage value and external insulation of walls is not possible. If internal insulation is applied, careful hygrothermal assessment has to be carried out to avoid critical moisture conditions in the wall leading to failure modes. Insulation material market is dominated by petrochemicals or non-renewable natural materials. Yet development of bio-based thermal insulation materials is increasing and some of them successfully entered the market. EU Bioeconomy Strategy enhances use of bioresources to increase their added value. The main goal of this research is to assess applicability of innovative bio-based pine needles insulation material that is produced based on bioeconomy principles as internal insulation material for historic massive walls. Results show that studied material is highly porous, has high moisture transfer, storage capacity, and is good hygric regulator. Lime treated material has no mold growth at relative humidity 85%. Even if insulation material is treated with lime, heat savings have to be sacrificed to reduce critical conditions for mold growth.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 186〈/p〉 〈p〉Author(s): Min Zhou, Bo Wang, Junzo Watada〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Unit commitment is an optimization problem in power systems, which aims to satisfy future load at minimal cost by scheduling the on/off state and output of generation resources like thermal units. One challenge herein is the uncertainties that exist in both supply and demand sides of power systems, which becomes more severe with the growing penetration of renewable energy and the popularity of diversified loads. This paper proposes a rolling horizon model for unit commitment optimization under hybrid uncertainties. First, a probabilistic forecast approach for future load and wind power is given by exploiting the advanced deep learning structures, 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.svg"〉〈mrow〉〈mi〉i〈/mi〉〈mo〉.〈/mo〉〈mi〉e〈/mi〉〈mo〉.〈/mo〉〈/mrow〉〈/math〉 long short-term memory neural networks. Second, a Value-at-Risk-based unit commitment model is applied to decide the on/off state and output of thermal units in the next 24 h. Then at each time window, the distributions of future load and wind power are dynamically adjusted by a rolling forecast mechanism to involve the real-time collected data, whereafter a look-ahead economic dispatch model is applied to improve the output of units. Finally, the effectiveness of this research is demonstrated by a series of experiments. Generally, this study introduces a fundamental way to integrate forecast approaches into classical unit commitment optimization models.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 186〈/p〉 〈p〉Author(s): Xiaofei Deng, Jian Yang, Yao Sun, Dongran Song, Xiaoyan Xiang, Xiaohai Ge, Young Hoon Joo〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Precise estimation of effective wind speed plays an important role in the advanced controls aiming at maximizing wind power extraction and reducing loads on turbine components. This paper proposes a sensorless effective wind speed estimation algorithm based on the unknown input disturbance observer and the extreme learning machine for the variable-speed wind turbine. First, aerodynamic torque is accurately estimated through an unknown input disturbance observer where the rotor speed is the measured output of the wind turbine drive train system. Then, the aerodynamic characteristics of the wind turbine are approximated by an extreme learning machine model based nonlinear input-output mapping. Last, effective wind speed is estimated based on the extreme learning machine model, using the previously estimated aerodynamic torque by the unknown input disturbance observer, together with the measured rotor speed and pitch angle. The proposed algorithm is validated by simulation studies on a 1.5 MW variable-speed wind turbine system. To evaluate the performance of the proposed algorithm, a detailed comparison with the Kalman filter-based method has been made. Comparison results clearly demonstrate that effective wind speed estimated by the proposed method is more accurate than that by the Kalman filter-based method and that the computational efficiency is higher.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 186〈/p〉 〈p〉Author(s): Juan M. Lujano-Rojas, Ghassan Zubi, Rodolfo Dufo-López, José L. Bernal-Agustín, Eduardo García-Paricio, João P.S. Catalão〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A computational model for designing direct-load control (DLC) demand response (DR) contracts is presented in this paper. The critical and controllable loads are identified in each node of the distribution system (DS). Critical loads have to be supplied as demanded by users, while the controllable loads can be connected during a determined time interval. The time interval at which each controllable load can be supplied is determined by means of a contract or compromise established between the utility operator and the corresponding consumers of each node of the DS. This approach allows us to reduce the negative impact of the DLC program on consumers’ lifestyles. Using daily forecasting of wind speed and power, solar radiation and temperature, the optimal allocation of DR resources is determined by solving an optimization problem through a genetic algorithm where the energy content of conventional power generation and battery discharging energy are minimized. The proposed approach was illustrated by analyzing a system located in the Virgin Islands. Capabilities and characteristics of the proposed method in daily and annual terms are fully discussed, as well as the influence of forecasting errors.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 186〈/p〉 〈p〉Author(s): Ali Ahmad, Syed Abdul Rahman Kashif, Muhammad Asghar Saqib, Arslan Ashraf, Umar Tabrez Shami〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The use of inefficient household appliances and their poor power quality results in energy wastage in residential buildings. These appliances also force the power system to operate at low power factor which results in an ineffective energy utilization. This paper reports the energy consumption pattern of mostly used household appliances individually and collectively over a year. Their power quality parameters are measured through experimentation to calculate the reactive energy consumed by household appliances. This paper also proposes the reactive energy tariffs to enhance the awareness among domestic consumers to make efficient use of household appliances. Currently the reactive power management is being dealt for only the industrial consumer by imposing low power factor penalty. This research estimated that Lahore Electric Supply Company (LESCO) can generate a revenue of almost 150 million US dollars in one year from household consumers by applying three part tariff scheme on reactive energy. By improving the power factor it is estimated that an energy conservation of 1.1 × 10〈sup〉9〈/sup〉 kWh per annum is also possible. Thus the proposed tariff for reactive energy encourages the domestic consumers to get involved actively in energy conservation while enabling the energy utilities to transfer more active energy to consumers without the expansion of the distribution network.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 186〈/p〉 〈p〉Author(s): Wei-Mon Yan, Chen-Yu Chen, Chia-Hao Liang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Applying metallic bipolar plates on high temperature proton exchange membrane fuel cells, which are practical for stationary applications, is a considerable option to reduce the cost and to improve the specific power of this type of fuel cell. To understand the life issue of the high temperature proton exchange membrane fuel cells with metallic bipolar plates, the performance degradation phenomena with graphite, uncoated 304 stainless steel, and gold coated 304 stainless steel bipolar plates are studied and compared. The experimental results show that the order of performance degradation rate is uncoated 304 stainless steel 〉 gold coated 304 stainless steel ∼ graphite. The faster performance degradation of the high temperature proton exchange membrane fuel cells with uncoated 304 stainless steel bipolar plates can be attributed to the dramatic increase in the ohmic resistance, which is due to the formation of ferric oxide and iron phosphate on the metal surface. In addition, gold coating peels off from the stainless steel bipolar plate after a 432-hr operation. A coating layer with an improved life is still needed to further extend the operating life of this type of fuel cell.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 186〈/p〉 〈p〉Author(s): Xin Shen, Dexuan Zou, Na Duan, Qiang Zhang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this paper, an efficient fitness-based differential evolution (EFDE) algorithm and a constraint handling technique for dynamic economic emission dispatch (DEED) are proposed. In EFDE, there are three improvements compared to the standard differential evolution (DE) algorithm. First, an archive containing the current and previous population is established to provide more candidate solutions. Second, two mutation strategies are used to generate mutant individuals, where the population similarity is introduced to choose a suitable one between DE/rand/1 and DE/best/1. The fitness-based mutation operation is efficient to balance the exploration and exploitation ability of EFDE. Third, EFDE adopts a random-based mutation factor, and the crossover rate with the learning ability is developed to produce more excellent solutions. In addition, the infeasible solutions can be effectively avoided by the proposed repair technique. Four cases are selected to judge the performance of the proposed EFDE and constraint handling technique. For the fuel cost and emission minimizations of four DEED cases, a normalized approach (NA) is used to help EFDE to find the best compromise solutions in the evolution process. According to the simulation results, EFDE exhibits a huge advantage in comparison with the other approaches for the single-objective and multi-objective optimization problems.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 186〈/p〉 〈p〉Author(s): Krishnamoorthy Murugaperumal, P.Ajay D Vimal Raj〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Human work has been automated and replaced by various smart appliances at residential buildings with an objective to save time and energy. So, there is a massive upsurge of energy consumption everywhere and in due course, it resulted in increased electrical bills than before. In order to meet the growing utilization of more electricity by consumers at residences, internalization of renewable energy systems are firmly recommended for a better transformation. Hither, the IEMS is principally aiming to truncate the rate of electricity bills to consumers. Likewise, scheduling the usage of smart appliances and implementing load management practices prudently, a peak load reduction can be certainly accomplished by effectively using Solar Power, Batteries and Utility Grid. Already existing TOU tariff is employed in the process along with restructured components and renewable resources to manage the loads of different smart appliances according to their usage priority at different times of a day. This automated system is able to manage multiple heavy loads smartly with the help of renewable energy resources even at peak hours of a day.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 186〈/p〉 〈p〉Author(s): LiPeng Zhang, Wei Liu, Bingnan Qi〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A multi-mode coupling drive system has been designed and controlled to improve the dynamic characteristics and fuel economy of plug-in hybrid electric vehicles, which also can make full use of the configured superiority of centralized drive systems and distributed drive systems and avoid their structural defects. The configuration evolution process, working mechanism and drive modes of the multi-mode coupling drive system are introduced. The powertrain model is established for the target vehicle. Based on Charge Depleting-Charge Sustaining energy management strategy, an Electric Vehicle-Charge Sustaining energy management strategy is developed. The Improved Real-valued Genetic Algorithm is used to optimize the system structural and control parameters, it can help prioritize the drive modes which are based on the proposed energy management strategy. While ensuring the vehicle dynamics, the best energy allocation is achieved. The results show that comparing with a series distributed drive hybrid system and the intelligent Multi-Mode Drive (i-MMD) hybrid system under the NEDC condition, the 100-km fuel consumption of the optimized multi-mode coupling drive system is reduced by 16.52% and 15.40%. Respectively, it further proves the superiority of the drive system in improving vehicle economy.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 186〈/p〉 〈p〉Author(s): Jian Liu, Caifu Zhong〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Driven by the booming of electric vehicle (EV) market, the cost of lithium ion battery observes a remarkable decline which could significantly improve the capability of EVs in coordinating with the power generation from distributed renewable energy (DRE). This paper realizes that there are different EV-DRE coordination strategies while the costs and the associated infrastructure of these strategies significantly differ. An economic evaluation that compares these coordination strategies is therefore important. In this study, an economic evaluation is conducted among four EV-DRE coordination strategies. It finds that the cost of power supply from demand side PV plus storage systems could be lower than that of power grid supply before 2025. Besides, although the smart charging is a cost-efficient EV-DRE coordination strategy in the short term, V2G could be more economically attractive in the long run due to its capacity to fully realize the potential of on-board EV batteries. This paper also identifies the key barriers that EVs and distributed storage are facing in participating in the current electricity wholesale market in China and provides policy recommendations in terms of electricity time of use (TOU) tariffs, market thresholds and metering issues.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 186〈/p〉 〈p〉Author(s): S.N. Sazali, K.A. Al-attab, Z.A. Zainal〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Air-blown gasifier suffers from lower heating value of producer gas (PG) compared to steam gasification, but at the expense of the addition of steam boiler for the latter. The performance of an air-blown double walled downdraft biomass gasifier was characterized experimentally. Air fogging unit was added to the annulus of the gasifier allowing for superheated steam to be generated as additional oxidizer. Steam-to-biomass (S/B) ratio has been introduced to investigate the optimum amount of injected water needed to produce the optimum quality of PG. Comparisons were made on the composition and heating value of PG with and without water injection which were analysed and calculated with the aid of gas chromatograph. Highest heating value of PG was 4.72 MJ/Nm〈sup〉3〈/sup〉 at S/B ratio of 0.2 which corresponded to about 10% increment. Various S/B ratios were investigated in this study in the range of 0.1–0.3. However, as S/B ratio exceeded 0.25, it resulted adversely to the quality of PG. The effect of water injection on tar contamination in PG was also investigated. Tar reduction was proportional to the amount of the injected water resulting in about 8% reduction at maximum S/B ratio corresponding to 0.65 g/m〈sup〉3〈/sup〉 tar yield.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 186〈/p〉 〈p〉Author(s): B. Zouzou, I. Dobrev, F. Massouh, R. Dizene〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The Darrieus vertical axis wind-turbine (VAWT) has been the subject of numerous recent studies aimed at improving its aerodynamic performance in order to locate it in urban areas. This article is devoted to the study of an original VAWT with variable-pitch and low tip speed ratio TSR which is favorable to noise reduction and can operate at low velocity wind. The aerodynamic performance of this turbine is studied experimentally in wind tunnel as well as by CFD. In order to obtain the 3D-flow field around the wind turbine rotor, the numerical simulations are performed by means of detached eddy simulation method (DES). The simulation of pitch variation is made possible by using sliding-mesh method. Thus a specially created program adapts the pitch depending on the blade azimuthal position during rotation. The obtained results show that adapted pitch blades are preferable because they permit to obtain a power coefficient Cp that rivals other VAWT in the case of 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.svg"〉〈mrow〉〈mi〉T〈/mi〉〈mi〉S〈/mi〉〈mi〉R〈/mi〉〈mo〉〈〈/mo〉〈mn〉1〈/mn〉〈/mrow〉〈/math〉. The maximum torque fluctuation during rotation is lower in the case of adapted variable-pitch compared to fixed-pitch and thus the maximum aerodynamic loads on the structure can be reduced. Moreover, the pitch adaptation leads to lower interaction effects between the upstream-blade wake and down-stream blades.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 186〈/p〉 〈p〉Author(s): L. Rodríguez-Penalonga, B.Y. Moratilla-Soria〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉In Spain, after almost a decade of delay in the construction of a centralised interim storage facility, the spent nuclear fuel (SNF) context has suffered a significant change. Thus, the aim of this article is to present the Mariño model, which analyses the costs of different back-end scenarios by means of the net present value and the material flows calculation, in order to re-examine the SNF management strategy for Spain and to help determine which alternative suits better this new context.〈/p〉 〈p〉The current strategy was analysed opposed to two direct disposal alternatives and a reprocessing option. The results show that the scenario of direct disposal without a centralised interim storage facility would decrease the current strategy costs about a 39%. Also, an alternative design for such facility could entail a 29% cost reduction. However, a reprocessing strategy could increase the costs about 140%, but if some assumptions of the scenario are changed, the costs could be significantly reduced. Additionally, an increase of the NPPs operational lifetime would decrease the levelized costs of all scenarios, which emphasises the economic advantage of longer operational lifetimes.〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 186〈/p〉 〈p〉Author(s): Satyansh Singh, Jyoti Prasad Chakraborty, Monoj Kumar Mondal〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The process parameters (temperature, residence time and heating rate) for torrefaction of 〈em〉Acacia nilotica〈/em〉 in a fixed-bed reactor were optimized using response surface methodology. Maximum higher heating value and energy yield, both at the same time, were obtained at 252 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.svg"〉〈mrow〉〈mo〉°C〈/mo〉〈/mrow〉〈/math〉, 60 min residence time, and 5 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.svg"〉〈mrow〉〈mo〉°C〈/mo〉〈/mrow〉〈/math〉/min heating rate. Both the parameters were highly influenced by temperature; whereas residence time and heating rate had minimal impact. The torrefied biomass obtained at optimum condition was characterized by proximate and ultimate analysis, thermogravimetric analysis, Fourier transform infrared spectroscopy and scanning electron microscopy. Moisture content, H/C ratio and O/C ratio decreased by 73.23, 52.94, and 46.22%, respectively; while fixed carbon and higher heating value increased by 75.54 and 18.62%, respectively, as compared to raw biomass. Fuel properties such as fuel ratio increased by 87.39%, while combustibility index and volatile ignitability decreased by 83.32 and 22.71%, respectively. Flow properties such as angle of repose, Hausner ratio, Carr compressibility index and cohesion coefficient decreased by 8.04, 6.20, 22.48 and 12.5%, respectively. Enhanced fuel and flow properties make torrefied biomass a suitable feedstock for pyrolysis and gasification and optimization of this process may facilitate scale-up and reduce operational cost.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 186〈/p〉 〈p〉Author(s): Aghiles Ardjal, Adel Merabet, Maamar Bettayeb, Rachid Mansouri, Labib Labib〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this paper, a fractional nonlinear synergetic controller is developed for efficient power extraction and operation of a variable speed wind energy conversion system. The proposed fractional nonlinear synergetic control scheme includes: (1) rotational speed regulation for maximum power extraction at the generator converter side through the DC-DC boost converter; (2) DC link voltage regulation and active-reactive power regulation, by controlling the direct-quadratic components of the current, for power transfer at unity power factor, at the grid side converter through the inverter. Analytical design of aggregated regulator has been used in the nonlinear synergetic control design with the introduction of a fractional macro-variable in order to increase the degree of freedom of the classical synergetic controller. The stability of the closed loop system using the macro-variable is guaranteed and a fast convergence can be reached through the design parameter. Experimentation, on a permanent magnet synchronous generator based wind turbine setup, is conducted to validate the proposed fractional nonlinear synergetic control system for operating the generator and the grid sides of the power system. Different cases are studied and the experimental results have shown that the system controlled by the proposed control method is stable and tracks perfectly the desired reference.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 186〈/p〉 〈p〉Author(s): Yan-Hui Feng, Zhen Zhang, Lin Qiu, Xin-Xin Zhang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉As a valuable byproduct of the iron-making process, blast furnace slag with temperature up to 1450–1650〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.svg"〉〈mrow〉〈mo〉°〈/mo〉〈mi〉C〈/mi〉〈/mrow〉〈/math〉 contains a tremendous amount of sensible heat. Dry granulation and waste heat recovery via a moving bed is an attractive alternative to the conventional water quenching method due to energy-savings and the reduction in water consumption. In this study, the extended discrete element method (XDEM) as a numerical simulation method is adopted to investigate the heat transfer characteristics of semi-molten slag particles in a moving bed. The solidification and cooling processes inside the particles are described using one-dimensional (1D) and transient energy conservation equations and the enthalpy method is used to describe the release of latent heat. The result is compared with a case in which the temperature inside the particles is considered to be uniform. The numerical results indicate that the convective and radiative heat transfer rate and the released sensible and latent heat are all higher when the initial semi-molten state of particles is considered, but the waste heat recovery rate of a particle won't make much difference. The results of this research provide a theoretical basis for the accurate industrial simulation of the heat transfer in a moving bed.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 186〈/p〉 〈p〉Author(s): Michal Lipian, Ivan Dobrev, Maciej Karczewski, Fawaz Massouh, Krzysztof Jozwik〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉An increase in the efficiency of Small Wind Turbines (SWTs) by aerodynamic optimisation of the blade geometry is limited (low Reynolds number influence). Solutions such as the Diffuser-Augmented Wind Turbine (DAWT) and the twin-rotor systems are of increasing interest. A diffuser promotes an increase in the wind mass flow rate through the turbine, whereas an auxiliary rotor enables extraction of the wind kinetic energy in the wake.〈/p〉 〈p〉The paper summarizes the measurements of wind turbine systems performance conducted at the Institute of Turbomachinery, Lodz University of Technology (IMP TUL). The research incorporated a spectrum of wind turbine configurations for open and shrouded, single- and twin-rotor systems. The objective was to compare the performance of the same rotor in different configurations. The influence of a low Reynolds number flow on the rotor performance is also discussed and quantified.〈/p〉 〈p〉The study shows that, while augmenting the wind turbine performance (as much as twofold increase), shrouding rises significantly the rotor loading. A remedy for that may be an application of the second rotor. Although it provides a rather modest efficiency increase (11–13% for the unshrouded-, 4–5% for shrouded turbine), it allows loads to be distributed more evenly on turbines.〈/p〉 〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0360544219315270-fx1.jpg" width="359" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 1 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 186〈/p〉 〈p〉Author(s): Runhua Jiang, Frank G.F. Qin, Baiman Chen, Xiaoping Yang, Huibin Yin, Yongjun Xu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Trigenerative compressed air energy storage (T-CAES) system, placed to energy demand, can supply power, heat and cooling load to users simultaneously. In order to improve the performance of T-CAES system, an advanced T-CAES system is proposed in this paper, in which a burner is added before turbine to further heat turbine inlet air. In order to cope with the variation of energy demand, three operation strategies of turbine considering off-design condition is presented to control output power of the T-CAES system: turbine inlet mass flow rate of air control (TIM), turbine inlet pressure control (TIP) and turbine inlet temperature control (TIT). Thermodynamic performance analysis in design condition of the proposed T-CAES system has been carried out, and off-design performance analysis and comparison of the T-CAES system under different operation strategies have been investigated. Comparing with conventional T-CAES, the total consumed power of the proposed T-CAES system is a 495.0 kW decrease, and the power efficiency improves 1.2%. The turbine output power and assessment indicators should be both taken account to determine the best choice of operation strategy. This research may provide a guide line for system integration and operation strategy of T-CAES system under off-design condition to improve thermodynamic performance.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 186〈/p〉 〈p〉Author(s): Yuan Zhuang, Guodong Zhu, Zhen Gong, Chenfang Wang, Yuhan Huang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Experiments and simulations were performed to investigate the effect of ethanol direct injection plus gasoline port injection (EDI + GPI) on engine performance. Gasoline direct injection plus GPI (GDI + GPI) was also tested as a reference to EDI + GPI. The experimental results showed that volumetric efficiency increased with the raise of direct injection ratio in both EDI + GPI and GDI + GPI conditions. The volumetric efficiency and IMEP of EDI + GPI were greater than that of GDI + GPI, due to the stronger charge cooling effect of EDI. Combustion process was improved by EDI when ethanol energy ratio (EER) was less than 42%, however further increase of EER led to the deterioration of combustion process. Simulation results showed that ethanol's high laminar flame speed played a dominate role to the improvement of combustion process. Although EDI negatively affected the equivalence ratio around spark plug, this disadvantage was offset by the high laminar flame speed of ethanol, resulting in shorter initial and major combustion durations. Simulation results also found that combustion process was deteriorated when EER was greater than 42%, which was mainly due to over-cooling and poor mixing of EDI. Regarding emissions, NO decreased while CO and HC increased with the raise of both EDI and GDI ratios.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 186〈/p〉 〈p〉Author(s): Yuting Wu, Zhiyu Guo, Biao Lei, Lili Shen, Ruiping Zhi〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Single-screw expander (SSE) has the potential to meet the high pressure ratio condition in small-scale middle temperature ORC system. In this paper, variable internal volume ratio (from 3.00 to 8.00), new methods for calculating mass flow rate and friction power are integrated into the structure-based SSE thermodynamic model. And the maximum calculation error of mass flow rate, volume efficiency and shaft efficiency is 2.8%, 2.1% and 2.3% respectively compared with the experimental data. Herein, the influence of internal volume ratio on shaft efficiency, shaft power, volume efficiency, intake/exhaust pressure loss and friction loss are studied. The optimal internal volume ratio and shaft efficiency for five working fluids (R123, HFO-1336mzz(Z), R601, Cyclopentane, R245fa) are obtained when evaporation temperature changes from 373 K to 463 K. The results show that the optimal internal volume ratio is not the bigger the better when SSE works at high pressure ratio condition, because intake pressure loss also increases with the increase of internal volume ratio. The optimal shaft efficiency increases with the decrease of friction power, but the optimal internal volume ratio is almost unaffected. Furthermore, reducing intake pressure loss is a powerful means to improve the performance of SSE with large internal volume ratio.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 186〈/p〉 〈p〉Author(s): Zeyu Chen, Qing Zhang, Jiahuan Lu, Jiangman Bi〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this study, a novel method for the construction of a driving cycle based on a two-layer optimization process is proposed with a case study in Shenyang, China. First, the statistical data is obtained and divided into many micro-trips, namely the speed profiles between two successive stops; then, three representative parameters are derived from the vehicular model. Second, the development of the driving cycle is transferred to an optimization problem, and a two-layer optimization method is proposed to construct the typical driving cycle. In the first layer, the optimal combination of micro-trips is determined using a genetic algorithm (GA) with varying quantity of micro-trips, whereas in the second layer, the best quantity of micro-trips is determined according to the speed–acceleration probability distribution (SAPD) and average energy consumption (AEC). The results indicate that the proposed method can produce a more representative driving cycle, 2.49% closer to the statistical data than the traditional Markov chain method. Finally, the established driving cycle is applied to power management design with three different vehicle types. The results indicate that the established driving cycle can help in reducing the energy cost by up to 19.8% under the real-world Shenyang driving condition.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 186〈/p〉 〈p〉Author(s): Prabhu Appavu, Venkata Ramanan M, Harish Venu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The dearth of fossil fuels and aggravation of pollution levels are key factors responsible for the search of novel alternative fuel mixture. Since late 20th century, several researches were carried out with minimized alcohol content blended with base fuel. Alcohols blended with diesel were called as binary blends while alcohols blended with biodiesel-diesel blends were called as ternary fuels. However, there is very limited work in quaternary blends (diesel-biodiesel-oil-alcohol) which aims at partially replacing fossil fuel to a greater extent. Hence, the current research work focuses on utilizing quaternary blends with varying pentanol concentration (10%–40%) with fixed concentration of oil (5%) and diesel (50%). Test fuels were experimented in a single cylinder diesel engine and the results were compared with diesel and biodiesel blends. Results were interesting as BSFC and BSEC were reduced with increasing pentanol concentration. Emission wise, HC, CO and smoke were reduced while NOx increases marginally for quaternary blends with higher pentanol concentration. Combustion characteristics revealed that 40% pentanol blending has maximized peak pressure with increased HRR and minimal CHRR. Overall, 40% pentanol addition in diesel-biodiesel-oil can be a suitable alternative fuel mix for improving the performance and minimizing the emissions with marginal compromise in NOx emissions.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0360544219315282-egi10VRS21MWTQ.jpg" width="500" alt="Image 1021" title="Image 1021"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 1 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 186〈/p〉 〈p〉Author(s): Kang Kang, Sonil Nanda, Guotao Sun, Ling Qiu, Yongqing Gu, Tianle Zhang, Mingqiang Zhu, Runcang Sun〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The optimization of microwave-assisted hydrothermal carbonization for corn stalk was conducted to study the effects of reaction temperature (122.7–257.3 °C), residence time (4.8–55.2 min), and biomass loading (0.98–6.02 g/50 mL H〈sub〉2〈/sub〉O) using the response surface methodology. The hydrochars produced from hydrothermal carbonization of cork stalk under different reaction conditions were characterized to understand their physical, chemical, and structural properties. Statistical analysis shows that the carbonization temperature is the dominant parameter determining the product yield as well as heating value and quality of hydrochar. Due to the interactive effects amongst the process parameters, hydrochar mass yield and heating value cannot be maximized simultaneously. The highest energy yield under the predicted optimum conditions of 181.9 °C, 39.7 min and 3.8 g/50 mL H〈sub〉2〈/sub〉O reached 80.55%. The higher heating value of 22.82 MJ/kg was observed at 230 °C, 45 min and 2 g/50 mL H〈sub〉2〈/sub〉O, which is 41% higher than that of the raw corn stalk. The characterization results reveal that the microwave-assisted hydrothermal carbonization is a viable process for producing hydrochar, which can be used as a direct solid fuel or auxiliary fuel.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 186〈/p〉 〈p〉Author(s): Xianbiao Bu, Kunqing Jiang, Huashan Li〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Single well geothermal heating (SWGH) can widely be used all around the world, no matter if there are rich hot water reservoirs. However, its promotion is limited due to long payback period. To reduce the payback period, the intermittent operation mode is proposed in terms of the commercial buildings. An experimental test for continuous heating is firstly carried out, and the extracted thermal output is 448.49 kW with the static payback period of 7.17 years. A mathematical model is then developed in order to simulate the performance of intermittent operation. The simulated results show that the extracted thermal output for intermittent operation is always greater than that for continuous operation due to having the heat recovery period. The extracted thermal output is respectively 619.12 and 587.51 kW in the first and the tenth heating season at the fixed injection temperature and velocity. The extracted thermal output can keep stable if changing the injection temperature and velocity, and thus the imbalance of the extracted thermal output among different heating seasons can be adjusted. The static payback time for intermittent operation is reduced to 5.16 years compared to continuous operation, which will speed up the spreading and application of SWGH technology.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 186〈/p〉 〈p〉Author(s): Marko Nagode, Aleš Gosar, Caoimhe A. Sweeney, Joris Jaguemont, Joeri Van Mierlo, Domen Šeruga〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉One of the challenging tasks related to lithium-ion batteries (LIBs) remains a comprehensive approach for battery behaviour modelling. An approach is presented that enables modelling the voltage-capacity response of LIBs that are subjected to variable temperature and current load histories. A detailed presentation of the developed macro-scale phenomenological model embedding the mechanistic properties of the Prandtl type hysteresis operator and the concept of the force-voltage analogy is made. The necessary input data preparation for the model calibration is also presented. Accuracy of the model is confirmed with experimental observations for both nested current load history at two different temperatures and for arbitrary current load history. The same measured data is used to calibrate and to simulate response of the first order Thevenin equivalent circuit topology in order to amply compare the obtained results.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 186〈/p〉 〈p〉Author(s): Takafumi Honzawa, Reo Kai, Akiko Okada, Agustin Valera-Medina, Philip J. Bowen, Ryoichi Kurose〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A large-eddy simulation (LES) employing a non-adiabatic flamelet generated manifold approach, which can account for the effects of heat losses due to radiation and cold walls, is applied to NH〈sub〉3〈/sub〉/CH〈sub〉4〈/sub〉/air combustion fields generated by a swirl burner, and the formation mechanisms of NO and CO for ammonia combustion are investigated in detail. The amounts of NO and CO emissions for various equivalence ratios, are compared with those predicted by LES employing the conventional adiabatic flamelet generated manifold approach and measured in the bespoke experiments. The results show that the amounts of NO and CO emissions predicted by the large-eddy simulations with the non-adiabatic flamelet generated manifold approach agree well with the experiments much better than the ones with the adiabatic flamelet generated manifold approach. This is because the NO and CO reactions for NH〈sub〉3〈/sub〉/CH〈sub〉4〈/sub〉/air combustion are quite susceptible to H and OH radicals’ concentrations and gas temperature. This suggests that it is essential to take into account the effects of various heat losses caused by radiation and cold walls in predicting the NO and CO emissions for the combustion of ammonia as a primary fuel.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 186〈/p〉 〈p〉Author(s): Oscar Pupo-Roncallo, Javier Campillo, Derek Ingham, Kevin Hughes, Mohammed Pourkashanian〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The diversification of the energy matrix, including larger shares of Renewable Energy Sources (RES), is a significant part of the Colombian energy strategy towards a sustainable and more secure energy system. Historically, the country has relied on the intensive use of hydropower and fossil fuels as the main energy sources. Colombia has a huge renewables potential, and therefore the exploration of different pathways for their integration is required. The aim of this study was to build a model for a country with a hydro-dominated electric power system and analyse the impacts of integrated variable RES in long-term future scenarios. EnergyPLAN was the modelling tool employed for simulating the reference year and future alternatives. Initially, the reference model was validated, and successively five different scenarios were built. The results show that an increase in the shares of wind, solar and bioenergy could achieve an approximate reduction of 20% in both the CO〈sub〉2〈/sub〉 emissions and the total fuel consumption of the country by 2030. Further, in the electricity sector the best-case scenario could allow an estimated 60% reduction in its emission intensity.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 186〈/p〉 〈p〉Author(s): Subhasish Das, Biplab Kumar Debnath, Rajat Subhra Das, Alessandro Stagni, Tiziano Faravelli〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The application of porous media in compression ignition engines has significant effects on its combustion behavior. In this work, a Computational Fluid Dynamics (CFD) analysis of combustion in diesel engine is performed for 100% load, and the effects of porous media addition in the combustion chamber are quantified. With a porosity of 66.7%, silicon carbide is applied as porous media of cylindrical shape in the modified piston bowl in the conventional engine. The combustion analysis outputs include average cylinder-pressure, temperature; Nitrogen Oxides (NO〈sub〉X〈/sub〉), mean mixture fraction, turbulent kinetic energy, total energy and modified Peclet number. The results of the CFD study for the cases of non-porous media are validated against the performed baseline experimental analysis, whereas porous media predictions are compared to the state-of-the-art studies available in the literature. In presence of porous media, the average peak pressure and temperature are found to drop by ∼26 bar and ∼550 K, respectively, as compared to that of non-porous media. Furthermore, NO〈sub〉X〈/sub〉 emissions are significantly reduced up to 97%. The generation of turbulent kinetic energy is enhanced by 86% for PM leading to an increment of ∼36% in the thermal energy conversion than without a porous media.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0360544219314562-fx1.jpg" width="266" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 1 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 186〈/p〉 〈p〉Author(s): Weijia Yang, Jiandong Yang, Wei Zeng, Renbo Tang, Liangyu Hou, Anting Ma, Zhigao Zhao, Yumin Peng〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉With the increasing momentum towards flexible power systems based on renewables, the role of hydropower has great importance, especially for providing balancing power. In this paper, a fundamental study on the operating stability of hydropower generating systems is conducted to reveal the practical characteristics for the newly emergent issue of ultra-low frequency oscillations. A unique study methodology is adapted by combing the theoretical analysis and the physical model experiment. In this paper, first, the set-up of the integral experiment platform for the transient processes of the pumped storage plants is presented. Second, a mathematical model of hydropower generating systems is built, and the theoretical stability analysis is conducted based on the Routh-Hurwitz criterion and the stability margin region. The model experiments related to the frequency stability of hydropower generating systems were conducted with reference to the stability region from theoretical analysis. The results demonstrate the sustained ultra-low frequency oscillations and frequency instability of hydropower units in experiments for the first time. Attenuation characteristics of the oscillations are theoretically derived based on the stability margin region, and then quantitatively identified by experiments. The experiment accorded with theoretical stability region within a reasonable tolerance that corresponded to the ±0.1 stability margin.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy, Volume 186〈/p〉 〈p〉Author(s): Qiuyi Guo, Zhiguo Zhao, Peihong Shen, Xiaowen Zhan, Jingwei Li〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Vehicle energy economy is affected by different driving styles of individual drivers. To improve energy economy of plug-in hybrid electric vehicles (PHEVs), it is of great importance to develop the driving style adaptive optimal control strategy. In fact, driving styles are often influenced and restricted by different driving cycles. Therefore, to recognize driving style more accurately, this paper decouples driving styles from driving cycles. Based on classification and identification of driving cycles, the accelerator pedal opening and its change rate in different driving cycles are analyzed and the fuzzy-logic recognizer is built to identify driving styles. Afterwards, the driving style adaptive optimal control strategy is realized by combining the recognized driving style with the equivalent consumption minimization strategy (ECMS) and adopting a hybrid particle swarm optimization-genetic algorithm (PSO-GA) to optimize the relationship between the driving style and the equivalence factor (EF). The effectiveness of proposed driving style adaptive control strategy is validated by real vehicle test, which indicates that, compared with the original ECMS, the proposed driving style recognition based adaptive optimal control strategy improves the energy economy by 3.69% in the New European Driving Cycle (NEDC). This adaptive optimal strategy provides guidance for incorporating driving style into PHEV energy management strategy to improve fuel economy.〈/p〉〈/div〉 〈/div〉